Selling is one option but maybe keep at least one knife if you have any. Even if gameplay is more important to you, having a nice knife just adds something to the experience. Like pulling it out between rounds feels different than default. If you do decide to keep one, bayonet types are pretty solid
https://follownews.com/the-best-bayonet-knife-skin-under-500-bayonet-freehand/. Freehand pattern especially looks good without being over the top. Sell the rest and pocket some cash from it. That way you get money for the skins you don't care about and still have something decent to use while playing. Best of both worlds really