Novice guy here so be Nice.

I recently came across a brand new in a box Yamaha Rx-V861 that my brother purchased some time ago. He never got around to even opening the box and now its mine.  I purchased a pair of B&W tower speakers 600 series and I need advice on speaker cable and anything else that you feel I should add?  My original plan was a budget of $3000, I got the receiver for free and spent $1800.00 on the speakers.  Thoughts?  Used amp? Cd player?  What say you?

Hook it up right now with lamp cord or whatever you got and start listening. Leave the receiver turned on 24/7 and pay attention, you should be able to hear improvement in smoothness and detail over the first week or so. You want to do this because if you want a system that sounds really good then from here on in you need to no longer buy whatever you think might be good and only buy what you have tried in your system and found to sound the best. Play whatever you have, play the radio if you have to, and leave it turned on even if nothing is playing. Just never turn it off.

What you need in terms of components: the Yamaha doesn't have a detachable power cord or you would want to budget for that. It does have a phono input, which means it has a phono stage, which means you have to decide whether you want a turntable or not. Plenty of budget turntables that will kill a lot more expensive CD players so might want to consider that. Either way you will probably want a CD player. Interconnect. And speaker cables.

With $1200 that would be in very round numbers something like:
$300 turntable
$300 CDP
$300 interconnect
$300 speaker cable

This isn't what you spend, this is just so when you go shopping you have some guidelines to keep you looking at the right stuff. You've already gone and bought speakers that are way out of line with the Yamaha but that's fine they'll be your "anchor" component and plenty good enough to easily hear and know when you bring home something good to try out. 

That's the most important thing from here on in: try it out. Never buy what you have not heard. Never! Make it your rule. If not in your own system (preferred) then compare as much as you can in the store. Cables and interconnects can make all the difference, but they get a bad rap because so many of them are crap and the only way to know is bring it home and that's a lot of work so nobody does it and then instead of blaming their own laziness they blame the crappy cables. Just know up front they are mostly crap and make up your mind to search out the good ones.The minute you do you will know it was worth the trouble.

WHAT you buy matters not at all. HOW you buy is everything.

Speaker cables: Could be dirt cheap from Walmart, or super expensive. I don’t believe in sonic differences, so I just buy for aesthetics. For less than $40/pair, I own these:

Are you the type that would use a CD player? I’m the type to rip my CD’s and then just stream it over Wi-Fi to my system.

If you want a CD player, since you’d want to use digital out anyway, it’d be hard to beat this for the price:

As for a Toslink cable, and again just for aesthetics, maybe this:

Please don’t listen to the other guy, spending the same amount on RCA cables as on the turntable and the CD player, that’s just silly.

Future purchase should be a subwoofer (or two), I recommend looking at Rythmik, HSU, SVS, and PowerSoundAudio. 
Oh, and if you want a universal remote (and have a computer to set it up), the Logitech Harmony line is great, I have the 650 and love it for being <$50.
On my lower end system I made my own speaker cable with 12 AWG pure copper low oxygen "lamp cord' as @millercarbon calls it. Put decent banana plugs on it and I'm happy with it. Can be done with little skill and no tools. Its a step up from the 18 awg stuff from Walmart anyway.

I think for immediate, low complexity, low expense enjoyment with good SQ, CDs and a decent CD player are very hard to beat. And there is a nearly endless supply of cheap used CDs out there. That is where I would start.

Then I'd look into ripping them. But that gets complicated really fast unless you drop some cash for an all-in-one ripping, storing, playing solution like the Blue Sound Vault 2i. About $1200. Many here will tell you that its DAC is no good though.

I currently use an old iMac with iTunes (free), XLD ripping software app (free), a $30 USB cable and a used Schiit Modi 2 Uber ($110). I'm listening to Steely Dan - Two Against Nature ripped CD right now through this set up and it sounds great to me.
Don't spend any money on cables right now.

I'd focus on speaker placement, and room acoustics. See GIK Acousutics website.

Find the manual to your speakers  and follow the instructions carefully about ideal placement.

Listen for the instruments being able to transition smoothly from L to R without gaps. Leave enough space to the outside of the speakers so you don't have early reflections. Throw carpets/throw rugs around the floor between and behind them and listen again.

That's where you should start.
If you want to spend money on surge protection, the $180 Furman is the best value and most reliable I know of:

I agree with erik, that Furman is an excellent unit and is very hard to beat for the money. I'll so far as to say it's better than many power conditioners in the $1000 to $2000 range.
Sell the receiver and get a better amp that suits your needs. Do you really need or want a monster 7.1 channel amp? What are your sources?
if i was just starting out and didn't already own a warehouse full of gear i would forego cd/vinyl/dvd and just stream from tidal or spotify--you can do this as cheaply as adding a google chromecast audio device for $25 (or get a bluesound node for $400-500)--you could also connect your computer to the receiver, which would also enable you to watch netflix, etc.
You can still get the Chromecast Audios but they are more expensive now than before they were discontinued..not sure why Google did that!?
Great audio add on device.For sure get a pair of Subs.the brands mentioned above will do a fine job for you.I have/had the HSU and currently SVS[PC2000 x2].and +1 on an external amp since it has Preouts.

I second room acoustic treatment. I’ve spent a ton on really good equipment and I’ve more or less decided to not buy any more equipment until I get my room figured out. Thankfully I bought everything with my future room size in mind which will basically double from 16x17 to 16x33. So just have to get that project started up....
Also- I found the addition of subwoofers, and then the upgrading of those subwoofers (SVS PB 1000 pair to a pair of JL AUDIO fathom f212v2 ) did more than upgrading my oppo, improving cables or power cords. But it’s all about what you like - I like feeling the music and filling out the bottom end and the first time I fired up the fathoms the smile wouldn’t leave my face. And it’s still there.  
How do you plan to use this system? You posted in the home theatre section so I presume it will be used mostly for TV/movies, but is that the case? What is the room like (option for full surround setup, closed or open concept, large or small, in an apartment with shared walls or somewhere you can crank it up without the cops being called, etc)?

Do you also plan to also use it for just music from time to time?...if so, how often and would it be more for background music, to listen critically while focusing on or getting lost in the music, to play loudly at parties, etc?

If home theatre is your main usage, and the room allows for it, I’d recommend expanding to a 5.1 system. That means adding a center channel, surrounds, and a subwoofer. You’ll find a surround setup far more immersive than just stereo, but it’s not the right call for every room. The center channel would ideally be matched to your towers or at least as close to them as you can get for your space and budget...B&W’s current 600 series is another $600, so it may or may not be worth looking at previous years’ models or something that isn’t a perfect match to free up money elsewhere if your budget isn’t flexible. Given your budget, I’d definitely save money on surrounds and get something cheaper than the current b&w lineup...consider used here too. I have built-in surrounds in our main family room to minimize the footprint, but that’s only an option if you own the home and can run the’s worth considering if aesthetics matter in your space though. You can often find open box in-wall speakers really cheap since they don’t include a speaker cabinet.

I agree with the subwoofers recommended above and have a SVS myself. The feel-it-in-your-chest sensation of those deep bass tones adds a lot of impact even vs large tower speakers. If not the swiveling your head around to look when you hear something behind you from the surrounds, the subwoofer provides the most “wow” moments for people new to good home theatre. 

I also agree that at this stage you shouldn’t spend much at all on cables. The sonic improvement of expensive cabling over cheap cabling is tiny compared to the benefits you can gain elsewhere at this point.

This is just one idea. Expanding to 5.1 will make TV & movies more enjoyable, but if you don’t have the space for a surround setup or are interested in streaming, more time focusing on music, or want to get into vinyl then your money can definitely be better spent elsewhere. $1200 could get you a lot of great options but it really depends what your goals for the system are.