Thread necro here ...
The best, usable powers in Traps are Caltrops, Triage Beacon*, Acid Mortar, Poison Trap, FFG, and Seeker Drones*. Web Grenade is not consistently helpful except when soloing and the trip mine / time bomb very hard to pull off in team play. Again, these are solo powers.
All of the good powers except FFG have relatively long recharge timers, especially Triage Beacon. With SOs you can get it down to where you can do Caltrops every fight, alternate Poison Trap and Acid Mortar between fights, and do Triage Beacon every 3rd or 4th fight. Seeker Drones is basically once every other fight with heavy recharge.
So the playstyle is essentially get down your drone and FFG before the fight, set your 1-2 traps when you know where the fight will be, maneuver the FFG into a good position, and then use your AR powers and secondary powers as needed.
I would get the good Traps powers first and slot them with 3-4 each before seriously investing in AR. The good traps powers have a noticeable impact on team play.
The basic AR powers are Burst and Slug, and you should take them and slot them.
Beyond that, it's a question of how much AR you want (AR has wonderful AoE potential) or whether you want to zero in on support powers (Medicine, Leadership, Experimentation). Since Traps doesn't have toggle powers (and you will eventually have set IOs reducing your traps powers' endurance cost) you can easily afford other toggles, stamina-wise.
I like my defenders to take support powers, so my build would probably have:
6 Primary powers (as above)
4-5 Secondary powers (burst, slug, and 2-3 of the AoEs)
2-3 Leadership toggles
3 Medicine (aid other, aid self, field medic)
3-4 Experimentation
2-3 in other pool (ancillary, travel, or Fighting most likely)