Stick insects are great! I have most experience with the two types you are referring to. The giant prickly ones aren't actually too sturdy - they have heavy bodies and weak legs which can make them fragile. You always have to be careful with sticks, they can lose legs easily - never pick them up, let them walk onto you instead. If you like the look of Indian sticks then get them - they are not much different from the pricklies except for the whole parthenogenicity (they are all female and lay fertile eggs) and the prickliness! I don't think either of them eat eucalyptus - it's poisonous for most things. I always fed them on bramble but you might want to google that.
I think you chose well but remember to be gentle and patient with these fascinating and peaceful animals. Good pets for a 14 year old? yo can't really beat an invertebrate. They take up little space and maintenance. Second up would be a passive beginner snake or lizard (eg leopard gecko, they are brilliant) and third I would choose a rat or house rabbit - they're more maintenance and can smell but they're robust and great pets if you do your research. I think you should stick with sticks though, they're easy when you have read about them and they're very engaging, plus they won't hold it against you if you don't pet them! Tips? I kept mine on my windowsill without a cage - just shoved some brambles in a vase and had them crawling about. It was wonderful, they didn't stray far from the windowsill. Make sure you give them a separate dish of water-soaked tissue paper, be careful not to take their legs off and make sure they can't fall into water from the vase you keep the plant food in. If they do lose a legdon't worry about it - they won't die from a couple of legs being broken off but be more careful next time as if they lose too many they will die.
I have kept sooooo many stick insects! :D I love them, they're fascinating!