Not all gems can be enhanced during rituals on starting levels. The higher your level is, the more valuable gems you can merge in the totem:
Level - Gem's maximum rating
1-5 levels - 50.000
6-10 levels - 100.000
11-15 levels - 150.000
16-20 levels - 200.000
21-25 levels - 250.000
26-30 levels - 300.000
31+ levels - 999.999

Your ability to merge gems also depends on the number of the dungeon you're currently in. If the totem says that your gem is too big to perform the ritual and your level matches the gem's rating, then you simply need to move to the next dungeon to get a totem with a larger capacity.