I am playing for free and I have 1925 HP currently saved up and I’m in a transition from going 2*>3*. Currently my roster is the following and my question is when/should I buy a cover for the 3*'s every time I have enough? Also if anyone has any advice on my character builds then I am open ears. Currently I am working on leveling up IM40 to 77.
Using your hp for roster slots and for shielding after your final push in PVP will get you further than buying covers - much cheaper to use a shield and secure yourself a 3* from placing then to buy one. The best time to buy covers would be if you have a 3* you like with 10-12 covers to finish them off, but even that is questionable for a free player.