the rewards for LOL will not really help you much so you can skip that for now. i would suggest you to complete Act 6. with your limited roster, you shouldn’t be exploring act 100% yet but you can take easiest path of each chapter. you can get more 6 and 5 stars from act 6 completion and more rank-up materials to build your roster.but also, because you have just reached cavalier so you don’t have to rush act 6 completion yet. you can attempt cavalier monthly event quest next month and you will get a lot of good rank materials and crystal shards.you can try variants if you have the necessary champs. your Guilly 2099 and Warlock will be helpful for Variant 3. variant 4 is also pretty easy if you have maxed champ from 1 star to 4 star.