The good news is EVERY trail on the Quantocks is lovely, and worth riding. Some are fast and grassy, others are rocky and a bit more technical.
One possible introduction is the Vertebrate “Classic route” which recommends Weacombe, Smiths and Somerton Combes as the “best” descents. PM me with an email address, and I’ll send you a gpx.
Holford Combe, and Shepherds Combe dropping from Bicknoller Post into Hodders Combe are (in my opinion) absolutely essential.
Other folks rave about Bincombe (I’ve only walked up it, in thick mud) and Frog Combe. I particularly like the fast descent heading north off Dowsborough Hill (easy) and the Old Devils Galloping Path (rocky).
It’s all good, so have a superb weekend. You’ll probably become a regular visitor, like me!