What type of mantis do you want? Lighting depends on the mantis. You can put an N. wennerae under metal halides, but I wouldn't put an adult peacock under that (it would develop shell rot most likely). A good diet includes several (3 or more) marine meats soaked in selcon once a week ( soak once a week, feed 2-4 times a week) and live shelled food once at least once a month or more preferably several snails or hermits all the time. Also some are more sensitive to water parameters than others. No heavy metals, nitrates under 20, temp 70-82 (may depend on species), PH 7.9-8.4, Calc normal levels etc. etc. Just make sure not to dose iodine as that can be more harmful than anything. Also check Roy's list and see what species is attractive to you. Most people recommend an N. wennerae. They are common, hardy, only need a 5-10 gallon tank and can be pretty active.
Dan