the earliest i've started the run through the rift is around level 10/11 with a small party. you can skip a lot of experience by teleporting directly to the rift when you finish the bluff, but the streamlined way i use for picking up some experience is....
use the "set teleport" book you get at martens bluff to set portal at the trang teleport machine. then teleport direct to the umpani - join up, buy spells, walk to the hogar cave, get the "return portal" book. visit uncle bela, use return portal to get back to the trang and then use the machine to get to the rift.
if i'm going for an early run, i'll often make direct for the templar challenges by avoiding any and all peripheral things in the rift (including the priestess rooms, the corpse rooms, the staff/key sequence, etc.), and run through the courtyard rather than battle. then i'll use strategies similar to scatter to get through the throneroom.
once you're a templar, the rapax area is easy pickings. HOWEVER, you do give up quite a bit of combat-earned experience and item drops this way, so it can undermine your long-term goals.
one final thought - if your party is level 12 or lower, the encounters at the rift are a lot easier. most notably, minimal encounters with warlocks and samurais - just beefcake
i've never noticed a lack of items shopping at ferros getting there early. can you be more specific, scatter?