I haven't played it as much, but I can give you some pointers. First of all, for mods, you want as many grenade mods as possible. Grenades are your easiest source of kills, and will help get Crown of Tempests going, so you want them up whenever possible. Second, for skill tree, they both work pretty well. I personally use the top Attunement because I'm in love with ionic blink, and Arc Web is very useful for crown of tempests. The extra chain lightning makes your grenades much more effective and get more kills on a bunch of grouped up enemies. The other skill tree is good too though, because your arc souls count towards crown of tempests! All you have to do is put down your Rift and let your arc souls get kills, and they will activate the Crown's perk. For grenades, I personally use either pulse or storm. The pulse grenade obviously does a lot more damage and can kill higher level enemies, but the storm grenade has a wider radius and so can damage more enemies for me to chain arc web with. But most people would say pulse, so just use that one or whatever seems right for you. This helmet makes you customize your playstyle a little bit as well. You can just go throwing grenades at one or two enemies if you want to get the best out of it, so save your grenade for big groups of enemies that you know it will kill. Also, if you can, try to make sure your melee gets a kill when you use it, otherwise it won't activate crown of tempests.