Play in the TP room.
Learn the meta of the format you are interested in (which decks and strategies are winning and which cards are being used).
Watch videos of the format you are interested in to learn about strategies and decks.
Keep up with the winning decklists on mtgonline.com
Exploit the weaknesses in these decks.
Keep in mind that being competitive requires you to have the best cards. If there is no other card with X power level / effect / efficiency, then you must have that card or you are playing with a subpar deck. That's not to say that there aren't rogue budget decks that can win, but think about this: even in Classic with a cardpool of over 10,000 cards you still need Wasteland
($30) to be competitive. There are budget alternatives, but there's nothing else that does what it does as well out of 10,000 cards. There are only 1,400 cards in Standard, so you'll have even fewer budget options.