I would save evo coins for your best (or favorite) players .. at least 4 stars. Bronze to silver is pretty cheap ( 2 tokens 40 gold) Silver to gold, 10 and 100 gold.. gold to plat is 50 and 300 (i think) Decide what level you want to live at and take it from there. If you draft a player you already have in silver he will automatically evolve.
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