Something I hear new players say a lot is how if they had better lands they would do better. There is no denying that this is to some extent true.
Say in standard you are playing a red/white deck, currently you'd want to play 4 Temple of Triumph, 4 Battlefield Forge and enough basics and maybe an evolving wilds or two if you need to be sure of getting a mountain for chained to the rocks.
I'll use Magic Madhouse prices as buying four of something is easier from a dealer. Temple of Triumph is just under five pounds there, that's one PPTQ entry, so you have a choice, cut a tournament or get 4 of them. Here's the thing though - how much knowledge and experience do you need about deciding on the scry decision for them to be genuinely better than the basically free wind scarred crag? They are 32p on magic madhouse, but they are going spare all over the place, gain a life doesn't help matters much, but could be better than an incorrect scry.
Battlefield Forge is a different kettle of fish it's 8 pounds but also currently out of stock, so getting a set is two tournaments, or four drafts, but it really is better than either of the others as you don't lose any speed - however new players often don't like to take the damage from one if they need the colour not the colourless. Generally you definitely want it above the other two, but only if you can play it correctly - though for both taking a damage and scrying you can only learn by doing, but maybe that's the time to proxy them and see if you can play it with friends or before, during and after at FNM or tournaments.
Another thing to note is that in current standard a tri land could substitute for a tapped land though it is likely to make for a slow two colour deck.
Playing two colour decks which have a fetch in the format is rather more of a problem, the blue/black fetch polluted delta runs about 12 pounds, moral of the story here is probably don't play a deck that needs them if you have to substitute a tapped land and tri colour decks are going to be a mega fail without a good mana base.
Fundamentally you'll get better at magic by playing more magic to a much greater extent than having better cards (though I'm not denying they will help), finding ways to play more magic without spending much money will help you save those pennies for other cards.
Ask other players how they think you could have played a game better - don't always trust them though, there are different opinions and if they did well today that could have been luck, but if you don't ask you'll never find out.