New player, interested in starting Romanians

Hello everyone! I'm a new player and I'm curious about the best way to start a Romanian Force. I recently purchased two starters: Hit the Beach and Kursk. I've noticed there are a few different Romanian supplements available, such as Brave Romania, Bagration Axis Allies, and Eastern Front. If I want to ensure I have all the correct cards, decals, and rules for a Romanian force, what should I buy? It also seems that a few of the Romanian tank destroyers are sold individually. Alot of list I found online use some of these .Are these made of metal or plastic? I would prefer to work with resin/plastic rather than metal.