MAKING AND DUPLICATING MOLDS - as a hobbyist is often a sticking point with newcomers. How does one make a mold (aka buck).? What materials to use and how does one decide what is best for their purposes. If you ask 6 people how to make or duplicate a mold, you'll likely get as many answers. Though there are basic principles for mold making, there's no one way to make a mold. As a hobbyist, economics often comes into play since return on investment is generally not the initial goal. Most newcomers to vacuum forming begin with a problem that can be solved with the vacuum forming process. What can determine what characteristics your molds will have is how you intend to use them. Let's look at what may determine your choice.
COST - Resins make great molds that last for a long time, but they also come with a pretty high price tag. Wood, or fiber board (MDF) can be much cheaper but your mold may not last as long. Everything in between, including 3D prints, vary in both cost and durability, you need to learn what is best for your purposes.
SPACE - Not everyone has the optimal space for certain types of mold building, after all we're talking hobby level. Your choice of mold may be determined by your work space. If vapors, noise or even dust are an issue in your workspace, this may limit you to what can be used.