gauss works aswell, i usually go marines because you need the barracks for the spartans anway, and getting the hogs out while making the gremlins is tricky. If they are fast enough you wont have time to get enough out.

If you do hornets, then you go all out hornets, and skip the gremlins and spartans.

You have to remember you only have so much time to counter this tactic. If you try to do to much, they will be at your base before you are ready.