I noticed that so far, you've started two threads about 'butt plugs for beginners'.
EF has a great search tool that gives you the ability to search for exactly what you want under: Shop - Sex Toys - Anal Plugs. You can then use the 'Refine By' feature to narrow it down even further based on the Safety Index/Material you're interested in, Price Range, Insertable Length, Diameter and Circumference.
They even have a section for beginner anal kits.
Check out the link.