welp if you buy a titanic its 250$ when they sell them via merchandise ( stuffed animal + code) the online price for a titanic ingame pet is pretty much the same... cheapest gems i found are like 60$ for 1b not sure if thats 100% accurate...
so i would probably go with something like 750 fg/100m ?
i mainly got some expensive enchants:
2x chest mimic ( current 1,4b each)
2x Boss chest ( 300m each)
2x Boss Lucky Block (300m each)
2x Super shiny (440m each)
48 Huge Pets some rainbow some shiny some more rare than others.... will only list them if youre interested