Ghost mantis, P. paradoxa, and the leaf mimicry is as good as anything in the insect world: an irregular crown, lobed limbs, and coloration that shifts between brown and green with conditions.
Small, slow, and unusually tolerant of communal housing for a mantis, which means a group display is realistic if you keep them fed. Undemanding humidity, easy on prey size, and generally regarded as the best first mantis.
Affordable and widely bred, with nymphs available in volume through the season. The lifespan cap of roughly a year governs everything, so buy nymphs rather than adults and expect to repurchase annually. Anyone quoting you a premium for a ghost mantis is quoting you for convenience.