I think the best are probably the 1st Edition set but I don't think there is much difference in actual play. The army lists are different in the 2nd edition but again not enough in practice to make much difference.
I bought a 600 point army for 1st edition but also I got some/most of the options I could get via the Political Flowcharts. Mostly this was just a matter of using up spare figures from packs I already was buying.
Thanks Nick. I picked up some regulars from Peter Pig at the Newbury show a week or so back (my first visit - it's a really good show). Not quite decided where I'll take them, but at the moment it might be colonial settlers...with a twist.