I am building a magic the gathering deck?

Most decks run about 24 land so in your case i would divide that number accordingly for how many cards use what colored land. for instance if you have more white cards than put in more white land etc. As far as cards go not only do you need more but there are to many x1. a good mtg deck runs around 4 of every card. 3 if the mana cost is high and sometimes 2 for plainswalkers and stuff. but just focus on putting more of each card in your deck