Depending on your local clubs favorite "version" of 3-gun rules...
limited is cheaper to start (irons or non-magnified optic, and uses pump shotgun)
tactical iron- (same as limited, but you can use a semi shotgun)
tac optic-one magnified optic allowed on any 1 of the three weapons, no bipod.
heavy metal- big bullets to show how macho you are. scores major.
Open- most $$, but generally the easient div to win as long as your gear does not fail (it often does) and you can use and do pretty much anything that does not violate range rules or course of fire.
so basically you'll havce to give up all other hobbies and relationships in your life cause you'll have to try all the divisions, and you'll need a complete loadout for each.
to be serious though... DONT spend hella bucks on your rifle's barrel- you'll kill it within a year or two. Green mountain all the way. Chrome lined 20" for under 200 bucks.
Spend hella bucks on your optics.