why not get an ipad mini, they have tons of indie games like Princess Pony... lol Ok, sorry for bad joke.
In terms of PC, you have a few options between the $400-600 price points in budgeting a DIY build. Unfortunately, you missed the biggest sales holiday during Black Friday and Cyber Monday deals last month that would have opened a lot more options.
The sub $500 gaming PC (w/ OS) is hard to budget for since it solely rests on what sales are going on day to day and what you are willing to compromise. It's not hard to build for, but you do have to keep a keen eye on sales and know what is good value, part for part.
You did just miss the decent
AMD budget box barebones kit from Tiger Direct yesterday: AMD 945 x4, Gigabyte 760g mobo, 8GB ram, case & 500w PSU for $150 AR. It's no show stopper, but throw in a $70 gpu, $80 OS, $50 hdd and you would have been set for $350 for a complete budget gaming system.
$500-600 will open a lot more doors in what you can get away with in terms of every day prices for a value gaming PC, but even then, you can still be dependent on sale prices to get your money's worth. For a build right now, I'd probably start around with something like this:
PCPartPicker part list
CPU: AMD Phenom II X4 965 Black 3.4GHz Quad-Core Processor ($84.99 @ Newegg)
Motherboard: ASRock 970DE3/U3S3 ATX AM3+ Motherboard ($69.99 @ Amazon)
Memory: Patriot Intel Extreme Master, Limited Ed 8GB (2 x 4GB) DDR3-1600 Memory ($31.99 @ Amazon)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($67.99 @ NCIX US)
Video Card: Zotac GeForce GTX 550 Ti 1GB Video Card ($79.99 @ NCIX US)
Case: NZXT Source 210 (White) ATX Mid Tower Case ($45.98 @ Newegg)
Power Supply: Corsair Builder 430W 80 PLUS Certified ATX12V Power Supply ($24.99 @ Newegg)
Optical Drive: Lite-On IHAS324-98 DVD/CD Writer ($14.99 @ Newegg)
Operating System: Microsoft Windows 7 Home Premium SP1 (OEM) (64-bit) ($89.98 @ Outlet PC)
Total: $510.89
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2012-12-05 07:07 EST-0500)
You get a decent quad core with a very nice 970 series motherboard that will allow you to take advantage of overclocking the CPU if you wanted to. You could save a few bones and get a cheaper motherboard based on the 760 chipset, but you loose the ability to overclock, specially when the black edition AMD chips have a great ability to OC easily and cheaply. You could settle with an 880 series chipset motherboard, but they seem to be around the same price range as the 970 right now, plus you have to be careful since a number of cheap boards only support 95w CPU's instead of the older X4 BE chips that are 125w.
Just as a note, I've seen way better prices for the 955/965 BE chips when paired as a combo with a motherboard. It's not hard to find weekly deals for the cpu's around 75-80 with an 880 or better motherboard for 25-45 that comes with the same features as the $70 970 board listed above. You have to look around and shop for it. Not uncommon to save $50 here.
I threw in any pair of 8GB 1600, cas9 1.5v DDR3 modules. You can find something for a cheaper price on most days, say around $20-25; cheaper if you went down to the 1333 speeds. Honestly, it really doesn't matter too much for a budget box like this as the goal is to get a working computer for cheap that offers great value. Other stuff that I threw in without too much thought is a simple 1TB 7200 drive for about 70 bucks and a cheap $15 optical drive. You could get more value if you went up to a 2TB drive for a few bucks more, but up to you.
I picked a nice NZXT Source 210 case. I personally have built a few PC's around it and i find it to be a great value at this price point over other $40-50 cases, but don't limit yourself to what I picked. Look around, there are tons of other cases like the Cooler Master HAF 912, Corsair 300R and like 10 more other cases. You could easily even cheap out and find a crappy $20-30 case if you wanted to or you could wait to find a better deal with sales.
Paired with the case is the Corsair 430w v2 power supply for $25. Its going to be the best value PSU at this price point as its the only 80 plus certified under $30 right now that I'd get. It routinely goes on sale for sub $20 if you wanted to wait, but it can shoot back up to its MSRP of $40-50 any day. Even at $25, its still a great value and a great performer; more power than you need in a budget box like this.
The video card is the last thing I wanted to talk about as its the most volatile priced item in the whole set. GPU choice can easily change back and forth hourly depending on what parts goes in and out of sale, at what price points/tiers and what games you expect to play and at what level of visual quality. Saying you want to play "indie" games doesn't add any weight to the gpu choice since that's like saying you need to get somewhere in something with 4 wheels and an engine. Very ambiguous.
You could even be tempted to go with an entirely different PC build towards an APU like that of the AMD FMx socket A series that combines a quad core X4 cpu and a decent entry level gpu core that mimics a $50 6550 card (or better) or cross over towards Intel's sandy/ivy bridge cpu's with their HD 2000/3000/4000 gpu cores in practically all of their cpu's now. On board graphics are no sloth's anymore considering you could play a game like dirt 2, crysis or even skyrim and batman at 720P at playable frame rates.
For this build, I picked a Zotac 550ti 1GB since its price right now at $80. I personally don't like the Zotac brand, but if we are going for cheap and value oriented, it will work. If you can wait for a deal (which I highly recommend), you can easily find an AMD 7750 or an nvidia 650 for about $70, which is about or more powerful than the 550 ti. The AMD 7770 was $70 during BF/CM deals though, which was steal. You could also look at this
MSI 6670 card for $50 AR that adds a good value and performance for the price point.
Anything less and you might as well use an onboard Intel HD 4000 gpu core capable CPU (i3 3225k $130) or the new AMD A10 5800k ($120) with its 7660 gpu core since either are more powerful than the simple and cheap display cards like the GT 520, GT 610, or AMD HD 6450 that make up most of the sub $50 gpu market.