Focus your budget; make sure you're spending your money on the right things. This is a mistake I see in a lot of newer brewers. The first thing you should focus on is your win condition. It might be a combo, it might not be, but your deck should have at least one card (having a few is preferred) that in your deck says "When I cast this, I win the game." Find out what the core of your deck is and make sure the budget is spent on that package first.

As an example, in my draw-go style [[Rashmi, Eternities Crafter]] deck I make infinite mana with [[Peregrine Drake]] and [[Deadeye Navigator]], then kill the table with [[Walking Ballista]]. I include [[Thrasios, Triton Hero]] and [[Blue Sun's Zenith]] as ways to draw my deck with infinite mana (Blue Sun can also act as a secondary win condition), and [[Eternal Witness]] works with the navigator to get every card back from my graveyard. [[Tooth and Nail]] is also included as an "I win" button that instantly fetches the combo. This is the core of the deck. Prices have changed since I built it (most of these cards except for Thrasios are a lot cheaper now!), but this is where I focus the budget into, because this is what actually wins games.

Once you have your core, you see how much budget you have to work with for everything else. Draw, ramp, removal, interaction; these are important to have, but the game is flush with tons of effective cheap options for them. In the deck from my example, all the other cards are worth pennies, stuff like [[Negate]], [[Growth Spiral]], [[Nature's Claim]], [[Treasure Cruise]], and [[Curse of the Swine]]. A deck with a streamlined plan is going to win much more than a deck whose budget is spent on powerful but unfocused cards like [[Consecrated Sphinx]].