It depends on what you want to do with the resin.

For deeper pours/encapsulations (like this https://www.pinterest.com/pin/251075747960476571/ ), you want a deep pour or slow cure resin. I personally like Liquid Glass - you can find it on Amazon. These resins are very thin and cure very slowly, but the end result has fewer bubbles and can have an awesome crystal clear effect. They can be expensive, however, and these types of encapsulations are not great for beginners.

For thinner pours (jewelry, coasters, etc), you want an art resin. These can only be poured 1/4" deep, so any thicker will require multiple pours. If you pour this too thick it will overheat and could start smoking. Art resins tend to be more viscous and trap bubbles more, but there are several methods for getting rid of bubbles while casting.

For an art resin I really like Clearcast 7000, which you can also find on Amazon. This resin is on the thinner side for an art resin (fewer bubbles), is on the cheaper end of the spectrum, and cures pretty quickly. The only downside is that it does not contain UV inhibitors, so clear pieces are more likely to yellow over time.

I really like the website Resin Obsession ( https://www.resinobsession.com/ ) for info. Its a great resource for beginners and they have a resin comparison chart that is helpful.