You may want to have two builds - one for fullblown support and one for solo. And for what I write its just what works for me the point is to have fun and do what you like.
Gravity - two types of holds, one immobilizes and slows with some damage over time (Crush), the other holds and slows with less damage over time (Gravity Distortion) You get a version of these for crowds/aoe (Crushing Field and Gravity Distortion Field). So two types of controls, one set for one target, the other set for groups. The group ones are pure gold. get those, slot them up to the hilt. your teammates will love you for you it. Great procs from IO sets. The first two are pretty much all you can offer at early levels, but dont fully slot them - they are pretty useless for teams later on, unless you solo. So keep those somewhat slotted but not all out.
next are damage powers- Lift and propel. Lift does more damage than crush but really it is a waste. I have never used it. Propel hurls funny stuff at enemies, can do some decent damage, but also has knockback, which messes with the holds. I get propel as a means to do so SOME damage when piling on AVs, but it is not really a thing I do much with and it has been been known to annoy tanks and scrappers. Some slots with the basic enhancement type but the sweet spot of grav are those AOE holds, Crushing Field and Gravity Field, especially with Rad.
Then we have three powers left I call funky. Dimensionalshift, Wormhole and the Singularity. Dimensional and Wormhole have two negatives that teams dont like. Wormhole, well, sends the baddies to another place in the room , which is the opposite of what crowd control is supposed to be, but for solo, its your best and fun bet. Dimensional shift is, well weird. I never get it. It makes the baddies intangible. They cant hit you but you cant hit them. UNLESS you or a teammate get into the field, then you can hurt each other. It only serves as an emergency assist if solo. So I dont recommend it.
Then the Singularity, your own black hole pet. Well, it LIVES TO AGGRO. So many teams hate it. And when solo I hate it. So I dont waste on it. I go for Rad powers and leadership/other powers. Now I dont know if homecoming has made the Singularity smarter - I just suffered so much and so many teams hated it I didn’t bother. Its worse that Katie Hannon. If you are solo it ccould be your tank and you hold for it except its still unstable. sometimes it leads othertimes it follows and it doesnt taunt like a tank. So I say pass. Summary - for grav get the four holds and propel. and slot the group holds to the teeth.
Rad - this is the sauce baby. With those Grav holds, you can rad the hell out of overthing, and add more.
The Heal power is awful. You will need it though as sometimes it keeps you alive. so slot with a couple SO heal enh. but dont waste time. It just doesnt compare to the defender heals.
You then get three types of debuffs. Two are togglles which means you hit a target and it stays running on that target. the ither is a one shot that slows and lasts a bit. These are great. They make an AV swiss cheese, even giant monsters weak. Cut time in half if not more. Each of the theee is unque.
Radiation Infection is a toggle. a must. makes the baddies miss. a lot. makes their accuracy mush. slot that puppy up.
Enervating field is a toggle. Damage debuff. Slot this up too except it doesnt get too many enhacement types. For both of these toggles endo reduction and range and the to hit debuff for Rad Inf is really all you need. Both of the toggles affect those around them.
Lingering radiation is a one hit slow debuff. Also affects baddies around them. Great for AVs. doesn't need many slots.
So key point - an organized smart team, which is hard to do over chat, has you hold a group, and you pick a target in the middle to unleash the debuffs, and they kill that target last. That is a fool proof strategy for wiping out a crew of baddies fast. If not ya try your best. maybe hitting three different targets. but these powers are key and they dont need much slotting. just endo management.
ACCELERATED METABOLISM. Yes please! Teams love it because it helps endo production and its not as movement nuts as Speed Boost. takes a long time to recharge so add a few emhancememts to fix that. also ad the endo modification enhancement, not the endo reduction enhancement. three recharge enh should make it under 3 min wait I think. GATHER FOR AM! is a common cry.
MUTATE. If you love the walking dead this is fun. Its your rez and the teammate comes back all buffed zombie style. Takes a while to recharge so slot like AM.
Then we have our funky last three. Choking cloud is your own personal hold. anyone around you chokes and is held. they sit there grabbing their throats. its awesome. slot it up.
Fallout. I get this. It explodes a dead teammate. Its your nuke. heavy damage. but it requires a teammate to die first. so use with caution. its the heavy artillery of all your powers tho.
EMP. A nuke that only affects robots. I get it. slot wisely. you only use it a few times here and there. Mishes w mechnics. That one part in Cimerora with all those robots. But a good team power.
So few gravity powers that are heavily slotted and many rad powers with less slotting. I have a blast. V. Mary on Indomitable. But once you get it down, you swiss cheese everything and the rest of the team plows away. even crazy brutes and tanks and blasters will be drowning you with chats to join their team.