Best way to level from 88-90?
And what is prefered level to craft some fcr amus/rings?

Baal run or join public/group TZ farming. Some Discord community groups organize TZ farm games that are private. Ditto on the Baal runs.



General rule of thumb, get higher level toon to craft ammy & rings. Look up this post done some years back - https://forums.d2jsp.org/topic.php?t=30598890

The TLDR versrion: "Use a character of at least level 93 to gamble and craft Amulets - then every Amulet has a chance to get +2 to [class] Skill Levels / Skills."

For rings its usually better to not do with too high lvl char,
But it depends if you care or not about making lvl 94 req rings.