Hey there, I just reached level 40 and would like to have your advice on what to upgrade since I do not know how common the high end items are. I am guessing I should only upgrade +7..+10 stuff? And also only those of the highest rarity of its class (3* Bracelet, 4* Ring etc)? Should I always sacrifice 10 items at once or is it OK to use just a few items? Is there ever a need to upgrade stuff of lower rarity but with a high +value?

Are these items good enough to upgrade or should I wait until I get stuff with +7 or higher?
- 3* Bracelet +4
- 4* Ring +3

Thanks!