C.P.
Don't rush things, what you're doing now is perfect. Let your son play with it, taste it, push it back out. Children who learn how to feed themselves, not having food shoveled in, have an easier time of stopping when they're full. The tongue-thrust and gag will go away when his body is ready for solids...it's not something you really have any control over. It's okay, tho! :)
Check out this info from Kellymom.com about when to introduce solids - http://www.kellymom.com/nutrition/solids/solids-when.html
Enjoy and good luck! :)