At level 20, the only Pro perks I may have unlocked are soh and hardline. I don't bother with Ghost Pro unless untill I've found a Sentry Gun. This past Prestige, with the double xp and all, I didn't find a Sentry till level 35 or so. So, I'll probably get Ghost pro by the time I'm about ready to Prestige. The other pro perk I shoot for, which isn't really needed as well, is Hacker Pro. Takes forever to get that 25 claymore/c4 kill. Near equipment kill is alot easier using the motion sensor.
Another set of perks that I've found to be extremely usefull in domination matches on certain maps are Flak Jacket + Tactical Mask. Berlin Wall B spot is awesome. I just lay on one of the sides next to B, and people keep throwing their nades, tubes, rpg's and I just laugh. They'll try nova gas, and I laugh even harder. When they run in front of B, I blast away. I did the same thing while covering B on Kowloon as well. It's the funniest thing. I should save these matches.
Also, If you get Flak + Tac Pro, you're immune to everything except bullets.