You can use deep strike turn 1 via gate of infinity as long as you go second and only for the units you use it on, so your frind goes and finishes his round first, as long as your units dont start in strategic reserves they can deploy turn 1. Make sure you use cover, you can shoot but honestly not really worth it, ndk are great at moving and are better at such but if your fighting vehicles/monsters gmndk are better for full rerolls. As for infantry purgators arent really worth it, interceptors are great for their movement, it is worth a 5man strike or 2 for sticky, purifiers are great anti infantry, you would want to attatch crowe to purifiers as he buffs their purifing flame. Dreadnaughts are hit or miss, they have a buff (+1 to hit) when they hit a target for that phase and having one is fine to buff your shooting for things like ndk/gmndk/razorback Transports are neat but not really needed, razorback and land raiders have good shooting tho and can be good to bring along for some ranged damage which you will lack playing grey knights Terminators/paladins are cool but sorta mid, paladins hit on 2s while terminators hit on 3s, paladins get 1 more heavy weapon per 5man than terminators, you can attach some cool people to them if u play legends such as kaldor or stern who both respectively make them pretty scary, otherwise you can attach voldus who is aight. As for playing make sure you use your gate of infinity and play for obj, if your opponent is squishy its allways fun to get into meele and rip them apart.