It can be quite a hard route if you make good use of the singletrack on Holmbury and Leith, you can get maps of the Holmbury trails from Nirvana cycles in Westcott and the Redlands trails on Leith are online, if doing it at the weekend you can get plenty of pointers from people on the way round.
The above route is pretty much the route I used to do a few years back but once I found where all the decent trails were I it meant I was going up and down Holmbury a few times and the same for Leith and was starting to find the climb up to Ranmore increasingly difficult the more extra trails I did especially if I popped up Pitch as well.
I always start in Westcott these days and flag the Ranmore bit, also I prefer to go go anti clockwise finishing with Summer Lightning all the way back to the A25.