Great beginnings on a custom Glock!!!
Guys will say, "do this...dont do this" but its your pistol, do what YOU like.
I have been a heavy Glock user since they came into the country and have taught defensive pistol courses at some of the big name schools, so here is my take
The stock Glock trigger is very shootable, with a good polish job its really not bad at all. Google .25cent trigger job and get after it.
I prefer the 5.5# connector in all my Glocks. The 3.5# gives the trigger break a spongy feel. I much prefer the crisper feel of the standard connector.
If you are going to use the gun for any kind of defensive use, stay away from the reduced power striker springs and/or the lighter strikers. Both will reduce the energy the striker hits the primer with and potentially cause reliability problems. I know they are popular in competition, but i wont trust my life to anything less then a full power hit by the striker.
The only other upgrade id recommend immediately, would be replaceing the stock plastic sights. They dont give a very good sight picture and ive seen countless sets of them fail (as in fly off the gun) during hard use. The new ones have a screw holding the front sight on instead of the original little rivet thing. Id still replace em as soon as feasible with a metal set of your choice
Other then that, get out and SHOOT the beastie