You can effectively treat this as a 2/2 with no other relevant abilities
I wish there was just a little more support for it, like some reasonable cantrips that it could turn into good cardsmaybe something like Electrolyzebut you never know what the future might hold for Battlefield Thaumaturge
Incapsula incident ID: 238000890050956415-37806947854849603
Two copies each of Jorubai Murk Lurker and Zof Shade, as well as Gargoyle Sentinel, all have activated abilities that can make use of extra mana
Theres not really a lot more to it the only real note is that if a currently conniving creature is killed, bounced, exiled, or removed from the battlefield in any other way in response to the connive trigger, you still get to draw the card (or cards) and discard a card (or cards), but youll have a tricky time putting the +1/+1 counter on a creature that is no longer there
Targets that work from anywhere are nice too such as Dread Return or Unburial Rites