Do most carbine courses require a chest rig or some type of battle belt set up?  
Second, is Haley Strategic still making chest rigs. Haven’t seen any in stock in quite a while.

Usually you'll at the very least need quick access to a reload.

You need some means of toting mags that you can easily access.  IMO the best option, from whatever maker, has Esstac Kywi inserts, or equivalent.  No velcro and no buckles.

But, get what you can afford.  A surplus LBV will work.

Most courses that Ive been to required some sort of ability to reload from be it a belt or rig. Lots of times for the course of fire a few mags in the back pocket sufficed. All depended on the objective of the course itself. Most fundamental courses a readily accessible mag from the belt worked fine.

I do have a different take on chest rigs or vests. Moving, running, climbing and crawling I've lost a number of mags with open top pouches due to poor retention during various body positions and movements. Crawling in particular. Since I've prescribed to the idea of velcro flaps for the majority of my ammo pouches and one or two quick access pouches with a Kiwi insert for a fast reload.

This is only my learning experience, and my take.