For a design patent (medical clothing item) is it better to file provisional patent first? then regular one? Also can we use other items out there to construct our product (as in pieces of it used differently and not in the same type application?)
If you are looking for a design patent, you should not file a provisional application. A provisional application cannot be used for priority for a design patent.
For example, MPEP § 1504.10 provides:
Design applications may not make a claim for priority of a provisional application under 35 U.S.C. 119(e).
Moreover, the Convention period for a design patent is 6 months, not 12 months. You could in principle file a nonprovisional utility patent application, then 6 months later file a design patent claiming priority to the nonprovisional utility patent. But that would likely be an expensive six month extension of term.
Alternatively, you could file a nonprovisional utility patent application, then subsequently file a design patent application as a divisional before the utility patent application grants. This would likely be even more expensive, since you'd likely need to draft a full utility patent application and prosecute it. But it would extend the term by a few years.
I would say to both yes. Filing a provisional has the advantage that you have time to craft the claims while getting the priority day. Since the change of the law of priority day recognition the provisional filing is almost a must, even if you have outlined claims. Using off the shelf components for demonstration does not violate other patents. The violation starts when you sell and use as a commercial mean.
A provisional patent application is always a great idea because it sets your priority date at that earlier time, as a non provisional application (NPA) often takes longer to draft. It is meant as a placeholder only though while you draft the "real" application (your NPA). So while your NPA can benefit from the priority date of the provisional application, the provisional by itself does not offer any protection, I.e. in the case you fail to file an NPA within a year of your provisional, the provisional is abandoned. So be sure to follow within a year! In fact some inventors might prefer to work in secret rather than starting that one-year clock after the provisional is filed.
So while filing a provisional is a great idea, it is not required. It is neither necessary nor sufficient for full-on patent protection, which is the right to exclude. And of course it is an added expense, so shoe-string budgeted inventors sometimes forego filing a provisional.
Regarding prototyping material, you can use different material than that described in the application. No problem. What will be protected is the invention as laid out by the claims. Nothing has to exist yet in the real physical world.