The decision to use or not use a pressure pot will steer your choices pretty heavily. Alumilite manufacturers a number of different products that are different resins, but mostly user friendly. Alumilite Clear Cast is an epoxy resin that claims it does not need a pressure pot. Alumilite Clear Slow is a urethane resin that requires a pressure pot. For deeper pours of resin that do not need pressure, controlling your stirring and pouring will go a long way to prevent bubbles being embedded in the cast, and some epoxy resins allow use of a heat source along the resin surface to draw out air and give you a better casting. Your depth of pour will also need to be considered. Some resins only allow less than 1-2 inches of depth in a pour for proper flow and curing, while others allow you to pour much deeper levels of resin. MAS, Alumilite, Amazing, Silmar, West Marine, are all considered good manufacturers of different resins - read the tech specs and make some initial decisions as to how to proceed. Odor will be a problem with some - I find Silmar products to have a pretty strong odor, so I don't use them, but you may have more room to pour than I do and there are a number of folks here that love Silmar, so again, read the tech specs.
As a starter, I'd look at Alumilite Clear Cast - easily obtained, easy to mix, and doesn't require a pressure pot. You don't address depth or size in your question, so this may not be the correct choice, but it is a good introductory resin that works consistently for many folks.
