So after a couple of sessions, my Explorator has a nice lump of exp. However, it seems Im quickly running out of things to buy within rank 1. Considering I start with most of the skills and talents from rank 1 anyway, is it just assumed that Ill have to invest deeply into the ability boosters as well as having all the skills and talents by the time I reach rank 2?

Yes. You could look into Alternate Ranks for some ideas about Elite Advances, but advancing abilities is something you'll have to do in Rank 1. It's also something you should do in Rank 1, because it's something that really pays off.

Cool cool ta

I figured that it was the done thing to up the stats as they effect EVERYTHING, just seemed like I was running out of things to pick up really quickly =P

If you have access to the Lathe Worlds there are some excellent Mechanicus alternate ranks in there that you and your GM would probably be able to work out a port to Rogue Trader for. Our Explorator started out as a Factor of the Lathes and rolled as the party face of failure. Good times.