Okay, you want my honest advice? $350 for Christmas.
Well, you say you're 18, which either means late High School, or early College. As such, that entire amount can go out on one single set of textbooks. So I'd say save your money for textbooks. Or class supplies, since those can get expensive too.
Or, you know, a tutor. Honestly, while I try not to wedge grammar-centrism into the ground, I feel like you would learn best to practice and refine your grammar. In college, you will need to take English 101 and 102, regardless of what major you're in, and likely more as well. If you expect to get anywhere in college, your posting habits won't get you very far in any class, especially if it's a class that involves essays.
Although, likely, you aren't listening. You have $350 that you want to squander away, not spent. Got'cha. Well, your profile doesn't tell me anything... At all... But your posts indicate a history in gaming, so I'm going to assuming you have at least one of the current gen systems, and I'll make suggestions accordingly.
X-Box 360
Live Arcade (N+, Castle Crashers, Geometry Wars), Dead Rising, Saints Row 1 and 2, Crackdown, Halo 3, Fallout 3, Mirror's Edge.
PS3
Dead Space, Saints Row 2 (If you didn't do it on the 360), Uncharted: Drake's Fortune, Valkyria Chronicles, LittleBigPlanet, Fallout 3, MGS 4, Mirror's Edge.
Wii
Megaman 9, No More Heroes, SSB: Brawl, Super Paper Mario
Subcategory, Virtual Console:
Super Mario RPG, Breath of Fire II, Harvest Moon, The Legend of Zelda: Link to the Past, River City Ransom, Sim City, Secret of Mana.
DS
Feel the Magic: XX/XY, The Rub Rabbits, Meteos, Castlevania: Dawn of Sorrow, Chrono Trigger, Front Mission, N+
PSP
Metal Slug Anthologies, Valkyrie Profile: Lenneth, N+, Patapon, Kingdom to Paradise, Ratchet & Clank: Size Matters, Secret Agent Clank, Beats