A great community that should be able to help you a lot more than Blocktopia is /r/buildapc and /r/buildmeapc. Oh, by the way, I definitely recommend building your own- It's a lot cheaper than getting a pre-built one. It's not that difficult either, almost as easy as building something out of Lego.
I'm not sure what country you live in, but I'm going to assume you live in America. In this case, here's a few great PC's around the $900 range, not including monitors, keyboards or mice:
http://pcpartpicker.com/p/pxTMXL ($595.77, I'd suggest a $120 SSD)
http://pcpartpicker.com/p/DnNzpg ($751,29, SSD recommended as well)
Also, check out this website:
http://www.logicalincrements.com/. It's amazing. Also a nice guide for people outside of the USA.
Here's a few general tips:
- Don't buy i7. There's no point, a lot of people buy it because i7>i5 but you won't ever need it.
- Don't get 4k monitors. Most games don't support it, most monitors aren't even 60ghz, and they're very expensive right now. 1080p 60ghz is probably your best bet.
- One of the best "buy it for life" mice is the g400s. It's pretty expensive, around $70, but will last you a long time. I've been using it for some time now and absolutely love it. Allows you to change your DPI as well.
- Get an SSD, at least 120GB. Use it for your OS and most-used software (e.g. steam) and games (e.g. Minecraft & Skyrim). It's a lot faster than a HDD and makes a gigantic difference.
- Use Windows 8.1. It gets a lot of hate, but apart from the goddamn awful Metro design, it's a huge improvement over Windows 7.
Here's a list of essential or very good software. Check it out and use your own judgment:
Winrar (some people prefer 7zip or similar. 30 day trial but you can still use it after that.)
Teamviewer
Google Chrome (Firefox is nice as well but Chrome generally has more addons. IE isn't as bad as people say it is but I'd still recommend Chrome or Firefox)
Skype
iTunes
Quicktime
VLC Media Player (Or Media Player Classic. Use one of these as your main media player, they're a lot better than the default)
Java
.NET
Silverlight
Air
Shockwave
Paint.NET (Image editor. You've got GIMP as well, you should decide which one you want)
Malwarebytes (the new GUI looks very scammy now, but it's amazing)
Spybot
Adobe Reader (or an alternative PDF reader, like the one listed below)
Sumatra PDF
Google Drive
OneDrive
Dropbox (a little note about cloud storage services: I'd recommend Google Drive over OneDrive, Dropbox, Box, etc., more free storage + google docs)
Everything (A better search thingy)
Bittorrent (qBittorrent is probably better and without ads)
CCleaner
Imgburn
YTD Video Downloader (download youtube vids)
Microsoft Office
Spotify
Audacity
TreeSize (See what's using up all your space)
Prey anti-theft
Bitdefender anti-virus (best antivirus IMO)
Clover (just give it a try. it's fucking amazing)
Notepad++
Duplicate Files Finder (never used this that much, but it's supposed to be great)
Less Msiérables
Virtual Clone Drive (IIRC no longer needed on windows 8 as it has this by default)
Classic Start (fuck metro)
ALSO, use Ninite to install a lot of software at once. It's fucking amazing.
Here's one of the greatest "How to build a PC" videos as well:
(part 1 of 3)
Can't think of anything else right now, but I hope this helped.
If you've got any more questions, feel free to ask.
EDIT:
dont get a cheap psu, you will regret it.
Don't screw it shut till you are sure it works. It angers the PC gods if you show such hubris.
Don't use hydrogen peroxide.
If it's your first time building, have the day clear. Could take some time.
Lots of awesome monitors and a good mouse will make you happier than just about anything else. again, g400s is amazing.
A mechanical keyboard is great if you have the money for it. Look into it,
http://www.logicalincrements.com/ has a pretty good section about it as well.
EDIT2: check here for more info
http://www.reddit.com/r/buildapc/comments/1s52pl/what_is_the_1_newbie_mistake_when_building_a_pc/[1]
http://www.reddit.com/r/buildapc/comments/yyu0x/bapc_what_were_your_first_build_mistakes/[2]
http://www.reddit.com/r/buildapc/comments/1vo53z/what_mistakes_did_you_make_when_building_your/[3]
http://www.reddit.com/r/buildapc/comments/x7jv1/what_is_the_dumbest_mistake_youve_made_during_a/[4]
http://www.reddit.com/r/buildapc/comments/15h2me/build_help_what_are_the_mistakes_a_beginner_can/[5]
http://www.reddit.com/r/buildapc/comments/141fqe/your_mistakes/[6]
http://www.reddit.com/r/buildapc/comments/1uz2e2/what_do_you_regret_after_building_your_pc/[7]
http://www.reddit.com/r/buildapc/comments/1b66te/1_tip_for_first_time_builders/[8]
Sources: my experience & reddit
EDIT3:
Quote from fiesta:
>>>> Third edit: Don't go buggering about paying for antivirus software: Microsoft Security Essentials is completely free.
Don't. MSE was amazing back in the time but these days it's just not enough. Get bitdefender, it often has free trials. A good free antivirus is Avast (it gets a lot of hate but it does the job). Also, honestly... You don't need an antivirus if you're careful enough. As long as you know your way around the internet & don't do stupid shit, you should be absolutely fine.
EDIT4:
If you don't yet, you should probably use Chrome extensions. I'll post some of the ones I use on here, check them out and see if you'd like them! However, don't get too many as it'll lag your browser. I'll bold all the extensions which are definitely, really, essential.
Adblock Plus (blocks advertisements)
AlienTube for YouTube (replaces youtube comments with reddit thread comments if available, suddenly you can go to YouTube without getting cancer)
Auto HD for YouTube (self-explanatory)
Chromebleed (tells you if a site is still affected by Heartbleed)
Enhanced Steam (makes Steam a lot better, huge recommendation)
Gif Delayer (delays playing gifs until they are fully downloaded)
Hola Better Internet (Access websites blocked in your country, company or school. For example, a video is blocked in your country? 2 clicks with hola and you can view it!)
HTML5ify (Forces websites like Amazon and Youtube to give you HTML5 media instead of wrapping it in Flash)
HTTPS everywhere (Forces websites to give you HTTPS instead of HTTP if available)
Imgur to gfycat (replaces animated gifs throughout the internet with gfycat optimized HTML5 videos, which load faster among other things)
imgur uploader (Right-click uploading of images and screenshots anonymously or to your imgur account.)
Linkclump (Lets you open, copy or bookmark multiple links at the same time.)
Netflix Enhancer (Show trailers, IMDb/RT ratings, and much more, on the Netflix page. )
Personal blocklist by Google (Blocks domains/hosts from appearing in your Google search results)
Reddit Enhancement Suite (a group of enhancements for browsing Reddit , fuckign amazing)
EDIT5: Here's a nice reddit thread which should be able to help you with choosing windows 7 or windows 8:
https://www.reddit.com/r/buildapc/comments/177us7/windows_7_vs_8/.
I would not recommend using a linux distro, as most games aren't compatible with them. I wouldn't recommend using mac either simply because mac is shit)
EDIT6: another vs thread, this one for i5 or i7:
https://www.reddit.com/r/buildapc/comments/1nuhv1/i5_vs_i7/