Ghosts (Phyllocrania paradoxa) are great and tame easily, and have a very exotic look but are a very hardy species - recommended for beginners too. Chinese mantids (Tenodera sinensis) are a great option as they are a naturalized species so can be captured in the wild (I saw two today). The Chinese mantids also grow large at about 4", which means they also are hungry pigs.
One of my favorites has to be Carolina mantids (Stagmomantis carolina) as they are a native species, and extra nymphs from a ooth can be released. They seem to have individual attitudes/traits, take to handling and various feeders well, etc. Likely though I have a soft spot for them as I got started in the hobby rescuing my first mantid from a winter freeze while at work. They do require a bit more care, but if you can mange humidity and feeding properly, I doubt you'll have problems with the species as it was my first.
Some great beginner mantid species though are African mantis (Sphodromantis lineola), Budwing mantis (Parasphendale affinis or Parasphendale argrionina), Chinese mantis (Tenodera sinensis), Double shield mantids (Pnigomantis medioconstricta), Ghost mantis (Phyllocrania paradoxa), Giant Asian mantis (Hierodula membranacea), and Griffin mantis (Polyspilota griffinii). Although some are not necessary listed as typical beginner species, they are all hardy, and seem to do fine even with beginners.
Have fun searching and getting started.