I can promise you that for the latter 2 you will not get anyone who will do it for $10. Too small population and much more difficult to carry since you already have to carry the people you match on your team. And Slayer is so boring, you're best chance at $10 is probably there. If you ever feel like paying a bit more I might offer services for Slayer. For MLG I'd be looking for more but would prefer to recover.
Depending if you willing to go up on your prices I have both a mlg and slayer booster I can help you get a 50. I'm a legit 50 fivestar in MLG, and have boosted some of the worst kids at halo to a mlg 50.