you need Lapis Strawberry from the 3rd Stratum Take Points (click here, Ctrl + F and enter the item name)
As you will see, it's a rare find and i think at this point i had Take skills of 10 and still didn't get too many, there are 2 Take points on Floor B12 so you can run around going to these and waiting for them to replenish is a good way to grind EXP (level 12 seems a bit low to me, i average 2 levels per mapped floor).
Also i'd invest in Focus, for every Level in this skill will allow the user (Arthur and Simon) will recover 1 TP only if they are at full health, since i normally have Simon in the front line this means Arthur could have Infinite TP with the basic Formulas, at a high enough level your TP Gain will be greater than your spend (at least for weaker Formulas).
I also remember Rosa having a cordial that's like her initial one but regens TP instead of HP but i always use the initial one or the one that up's health in rare cases.
Finally, i'd rush the queen, this way not as many eggs have been laid and since the Ant Queen and her spawn are weak to Ice, Ricky and Arthur can double up the damage for a turn or 2