Ficus make great first bonsai. They grow very fast and are difficult to kill as long as you them warm and wet.
Discussion
My first bonsai will be one I grow from seed. It will be the one I work on the longest. Every other bonsai I'll buy and work on will only be practice for my bonsai.
With that in mind I'm looking for a bonsai that grows slowly but is extremely rewarding in 50 years.