Considering that you'll be building quite far down the road, I'd say post again for help about 2-3 weeks before your intended build time. Prices fluctuate quite frequently in the PC world, so any build posted now won't be as relevant.
However, this build should give you a ballpark about what to expect performance wise.
PCPartPicker part list / Price breakdown by merchant
An SSD is pretty low on a $500 gaming PC's priorities, so I couldn't include it without a significant sacrifice for your in-game performance. For 1080p gaming, the 280 should perform respectfully and is more than enough performance for League and CS:GO.