That seems like a good initial version of a deck. Mostly you'll find that people cut their decks down to the minimum of 60 cards so that they draw their best cards more often. It's initially hard to cut down to 60, but you can keep making changes as you play the deck. Ask yourself at the end of the game, what did I have in my hand and not cast? Why didn't you get to cast it? Was it because it was too situational, you didn't get enough mana, or you just always had better things to do? What do you wish you had drawn? Also look at any creatures that you don't end up using for attacking or blocking. Was it because they just got outclassed, or was it just unlucky circumstances. After a few games try to cut some of the cards that keep staying in your hand or that aren't too useful once they are in play.
With faster decks that play lots of cheap creatures, you probably want to play around 23 or 24 lands in a 60 card deck. You have some expensive creatures that are 6+ mana, so you probably don't want to go below 24 lands. In any case, that's the same ratio as what you have now with 75 cards and 30 land, so just keep that ratio.
