Basically what the title is, I know that there will be some crew skills that can bring in credits mostly ones like bio which is pretty much always needed but are the others worth while ? Can I make money off them or am i better off just gathering and selling materials for money?

Clearly "crew skills" can bring in money, because, as you said, gathering materials in the field and selling them is a way of getting credits.

 

For *crafting* crew skills, probably your best bet between now and some time in February 2022 (when 7.0 finally launches) would be Biochemistry for stim/medkit/medpack consumables and reusables, with Artificers being able to sell top-end dyes for substantial sums compared to the cost of materials.

 

Aside from that, top-end Augments are another thing, and it's probably surprisingly lucrative to make small quantities of high-tier craftable railshooter space mission devices (Cybertech).

 

Armour, weapons and miscellaneous mod-objects are liable to be way too expensive to train up.