So 2k to big to learn on?
Good question!
2000 is about as big as we normally see around here, though 2500 is not uncommon. Teaching takes awhile regardless, because there is a steep learning curve to 40k, period. The first hurdle is the tallest, but then it gets easier.
Any point limit I think is fine to learn on, if you're in it for learning. I think it's a matter of the list. The more repetition in the list, the less likely it'll be a problem. For example, if you have 6 squads of Grey Knights in Heavy Bolter Razorbacks (with psyammo, of course), you'll obviously learn faster than having six differently equipped Troops and vehicles.