As you no doubt know, Alan Moore wrote issues 1-22 and 36. He also wrote one story out of three in Tom Strong's Terrific Tales 1-12. So of course, get all those.

Peter Hogan, yeah, I'd never heard of him either. But he's not bad. His issues of Tom Strong, #'s 23, 24 and 35, are all worth picking up, partly because they all have art by the original art team. Also, Hogan's special, "The Many Worlds of Tesla Strong," is a heck of a lot of fun. One of my favorite Tom Strong comics, and definitely the best non-Moore one.
Of what's left, issues 25-34 ... they are all non-essential. Personally, of this batch, I like the first two best (issue 25 is by Geoff Johns, and issue 26 has really great art by a guy whose name I can't remember).
I would avoid issues 27-34 completely. They pretty much get worse the higher the numbers go.