What you can do and what you should buy depends largely on what you want to get out of the game.
If you just want to play casually with friends it doesn't really matter what you get. If you like big multiplayer games you can pick up copies of the Commander 2014 decks to get started playing Commander/EDH, you should be able to find them at stores like Target or Wal-Mart in addition to game stores. If you are just wanting to play 1v1 Duel Decks are a good place to go the most recent one is Speed vs. Cunning or you can get more intro packs like the Rakdos one you already got, again these products are at stores like Target in addition to game stores. You mentioned that you don't have a LGS to play at, but you should still be able to find somewhere to play whether it is at school in the cafeteria, at the local library in a study room (depending on how sound proof they are), or at a friends house.
If you want to start playing competitively there are 2 things you will need to decide. The first is where you are going to play, you mentioned you don't have a LGS, but is there somewhere nearby that you could travel to even if it isn't very often? The second is what format you want to play. This depends on a combination of what formats are supported where you play, for example at my LGS they never have Legacy or Vintage tournaments so I have no need to make a deck for those formats but they do play Standard and Modern so I do have decks for those ones, and what you can afford, generally Standard is the least expensive format and they get more expensive the larger the card pool.
If you do play competitively I would recommend playing Standard since you seem to be on a pretty tight budget and there is actually a good Red Deck Wins deck that you should be able to build for around $30. Once you have this deck if you do well enough you should be able to start building up your collection so that you can play other decks, and other formats.
If you don't find anywhere to play with people in real life there are 2 official way of playing Magic on you computer Duels of the Planeswalkers and Magic: the Gathering Online (MTGO). Duels is primarily a single player game, it has a limited card pool and only allows you to play against certain other decks, but is pretty fun and much better than no Magic. MTGO is a lot like paper Magic, just on a computer. You have to buy all of the cards that you want to play with, but you have pretty much every printed Magic card available to play with. I personally haven't play on MTGO but I have heard that it is a lot of fun once you get the hang of the interface.