magic the gathering would u recommend?

You never want to increase the size of your deck; it should always remain the minimum amount allowed in the format. But that doesn't mean adding more colors is a bad idea. You just have to pick and choose what to remove.

Going multicolor:

Pros:

--Each color has its own set of strengths and weaknesses. Adding a second color allows you to cover the weakness of the first color with the strength of the second. Or it can give you more options to amplify the strength of your first color with a similar strength of the second color.

Cons:

--There's always the chance that you'll have spells to cast of one color and a lot of lnds in play, but not enough lands for that color to be able to cast them. multi-color lands like Alara-block's Tri-lands, M10 and M11's Dual Lands, and Zendikar's Sac-lands can all help with balancing this, but it is still a risk, and most ways of managing this come with a downsize in life cost or coming into play tapped.

Thats not really a problem, having to colors makes higher cards harder to play, but also makes your deck harder to predict. So to make a good mixed deck, add some lower color specific cards, some colorless and only a few high cost colored cards.