Which would give me better training and chance of being deployed with Marines, reserve Fmf Corpsman or active?

I will be enlisting in the Navy shortly. I would like to enlist as an fmf Corpsman and was told by one that the only way to be guaranteed going fmf and working with Marines is to get it in your contract by enlisting in the reserves. What exactly do the reserves entail? After finishing basic, and "A" school (and fmss?) would I become active duty? I would like to go active but would rather have fmf Corpsman in my contract. Seeing as how 4 of my closest friends are all Marines I can think of nothing else as motivating and worth my while.