Tom

Tom is very costly. 15 jems for one day? Seriously? At first he used to work for free. How rare the jems are!!!

The time period he works for free is just a free trial so you can understand how Tom is used. The trial occurs at level 14 and is 3 days.

i didn't appreciate my Tom when I first had his services. However, you learn how to get by without using him too often as you learn your farm.

Also, as you get more machines and fields it is easier to keep supplies. Gems are not on every corner but this game is one of the most generous with their premium item that I have come across, so gems collection is not too troubling.

Finally, having Tom run to find some of the items that you need and can make later is well worth the 15 gems. I will spend it every couple of weeks (watching videos gives me this many gems) and Tom will get me diamond rings (costs a gem to make), maybe some mining tools (you can find gems while mining) and possibly blankets or some other time consuming/multi step product.

Learning Tom is fun, I bet there is a more in depth use message somewhere.