IMHO the better bits on Dartmoor are not in & around Oke – soz – unless you like northshore stuff which are in Abbeyford Woods.
Get yourself down to Princetown & ride down to Burrator & back. Trailmonkey off here guided the MBR guys recently on a selection of routes starting at Princetown, you may need to dig out the edition with them in.
There is also great riding round Lustleigh Cleave but you may need to have a local to show you where the best bits are, post up on here asking for a local guide for the day or advice on a route.