Even F2P players can enjoy it

Ads are optional, and if you play regularly, you can get most of the pulls and events are frequent, so you can just use them. You have to summon towers with diamonds, but you can get diamonds by consistently running dungeons and ranking up, so you can get them as rewards and summon. Removing ads makes it convenient, but it's optional. Equipment, relics, pets, and mounts have changeable options, so buy change stones when you see them. For guilds, join one with a high guild level to unlock more items in the guild shop. If you join an active guild, they'll clear the guild dungeons for you, so you can slack off. Upgrading towers might be the priority, but surprisingly, I want to focus more on summoning and upgrading characters. Builds used to be 'octopus' but they got nerfed so hard after patches that I can't recommend them. There's an official cafe, but the admin is weird and nerfs builds if users reveal them. Having a high base tower level is fun for creating new builds. Even with a low tower level, if you have Thor or Pirate characters, you can handle most things. Agni is used a lot in the early to mid-game, so make sure to get them.