Ryuki is a good one, but the ending might leave you a bit sour.

Blade is my favorite Rider show. Lots of great story arcs, a good self-contained lore and really cool fights.

Erase this, wrong thread. My bad.

I say keep powering through Den-O because otherwise I'm just gonna say to work your way chronologically through the seasons. Maybe sample a few eps of another Pre-Decade season so you can understand the concept of the worlds in Decade.

Kamen Rider Black, and then Shin
Kuuga is fun too