You've basically got the essentials for any CQB skirmish style game. At this point, its a matter of choosing what direction you'd like to take your airsoft experience: whether you'd like to go to a MILSIM event, more outdoor playing, staying with CQB, etc.
Otherwise, I might recommend a good set of shoes. It doesn't have to be boots, unless you are planning to going outdoors, but a good pair of comfortable high-traction shoes will helps loads in CQB.
If your CQB skirmish arena is only a minute away from the staging area, then this next suggestion is less important, but having a hydration carrier w/ bladder & water would help as well.