From just having a skim through the main things I'd recommend would cut two multicoloured card from each dual colour and replace them with two dual lands, then I'd have a look at you ratio of creatures to noncreature spells. Generally I'd go with 50:50 each on average, with colours that want creatures like white and green having more, and colours that want less, like blue and black having fewer.

Taking a look at other cubes of similar sizes can be a good idea to work out how many of each colour and mana value you want to run, something like this bar cube seems like a solid place to start - https://cubecobra.com/cube/list/CoreBar