There are a lot of good ideas for mages!
1. If you buy a marine, create an arbiter above your mage(cloak).
2.If you buy a medic, create a medic for x secounds so it heals like only 25 hp.
3.Try to make something defensive. Lets say defense matrix, so if you buy a firebat spawn a science vessel with nrj for 1 matrix.
4.If you need something offensive try creating a defiler to cast plague, as it could be named as Drain?.
There are many many more of theese. Just use your imagination
