>>538571951
My 2 cents:

>"Older" supports:
McQueen and Rudolf are strong but are from the "previous generation of support" which only carried 1 gold skill, for that reason I find it really hard to recommend investing tickets/stones for these. Just use them as much as you can now, but consider them on their way to become somewhat obsolete.

Shakur has 0 tokui at 2LB (like yours atm), which makes her very unreliable. Getting her to MLB would make her more consistent, but just like McQueen and Rudolf, as good as she is, she will be replaced by a 2 gold skills stamina card in the near future, it's garanteed.

>Newer supports
Tamano only really gains more training bonus (5% and 10% at 3 and 4LB respectively), anything else is already there at 1LB (which you have).

Exact same situation here with Ai-chan: 5% and 10% training bonus at 3 and 4LB respectively ; anything else is already there at 1LB (which you have).

For Stego, 2LB to MLB would increase her starting bond gauge to acceptable level (atm it's 1 aka 0), meaning you wouldn't have to struggle as much to get her to produce rainbows, thus increasing consistency.

All in all I would strongly recommend to upgrade one of the newer cards as you're bound to not regret it.
(Use https://gametora.com/umamusume/compare to do this kind of analysis.)