The easiest message just includes an amount, a location and a rating hashtag such as: #fail #poor #good or #great.
This is optional, but can be helpful to learn how you might spend differently with various payment methods. Try hashtags such as #debit #credit or #cash.
You can add a description of what you bought. Anything that's not a hashtag or a recognizable date ends up as a comment. The idea is to help you remember what you bought when you review your spending.
You can also designate a spending category with arbitrary tags. Use tags for conventional budget categories and call attention to your values such as #family or #recharge.