Buy 1x AA 0.25 print core and 2x AA 0.8 print cores, and get 2x free spools of Tough-PLA and PLA.
AA 0.25 print core is suited for printing small details and structures.
2x AA 0.8 print cores allows you to print very fast using two build materials, or combine colors. Printed parts are also more durable when printed with larger print core nozzle.