My recommendation would be to get one good set with both metric & imperial plus some cheap sets. Supplement these with a multi tool
Depending on your marker there could be a manufacturers multi tool, eg dye or Tippmann. Most will do but those are designed to have all the essential tools for their marker models
These are always handy in your pocket, but bear in mind it may be a breach of the rules to posess a tool in the game fields. Especially in a tournament situation
Most often if you see a cheap set of one type they are usually metric, but sometimes you can up complete sets or imperials cheaply in yur local shops. Online there is anabundance of all