My 5 cents
Getting rid of IS should be the top priority - they are the most direct threat to the US and their allies out of these groups. Boots on the ground is not a good idea, but the good news is those are probably not necessary - you can undermine IS using good old intelligence, diplomatic and law enforcement methods:
- shut down their online propaganda machines
- find and shut down their recruitment
- destroy their logistical centers
- disconnect their international support (money, weapons)
- stamp down on their oil business
With the above, you can weaken the enough that the other groups would annihilate them. Other than that it's hard to support any other groups in the fight against Assad - this would effectively be a proxy war with Russia and you know how those go...