Hello and welcome to the forum
Sounds like you will have several helpers with your new pet.
Regarding species, below is a list I've put together over the past few years of beginners species, and of course the most common places to get them too.
Where to buy
You can buy mantids from the
classified section (see the
feedback section about the sellers too). Of course there are many great sites to buy mantids and related goods from online such as
BugsInCyberspace,
MantisPlace, and
MantisPets the most common and recommended for mantis themselves.
Beginner mantis species
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 can collect over a hundred locally in a few weeks here. 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 (again this is another species that can be found wild locally). 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 Flower mantis (Creobroter sp.), Giant shield.hooded mantis (Rhombodera sp.), 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.