I've got 2 R3 Tech Champions so far which is the fewest of any of my classes, so it feels reasonable that I rectify that imbalance. But I'm really unsure who will give me the most bang for my buck.

In the gameI am in Act 9 of Story Mode, work through Valiant EQ each month, finished Epoch of Pain, haven't touched Wheel of Fate or The Ordeal yet, and only done a single pass of Necropolis still - so those are all factors. Battlegrounds I typically inch my way into the Gladiator Circuit each season and then don't move, but I would like to go a bit further.
I do have a Tech Awakening gem, although I was somewhat thinking to save that for either potentially pulling Sentinel or Future Ant-man. Sig Stones I could add about 60 sigs to one of this lot.
I'd really appreciate some advice on who of this lot would be the most useful at R3 for the content I'm facing. Thank you