Hello, and welcome as well!
I must say (and I don't mean to be age-ist), you sound well versed for a 10th-grader/sophomore in high school. It sounds like you are very caring and would do a wonderful job with a snake once you learned all the ins and outs!

Firstly, I'd make extra-certain that your parents are comfortable with you having a snake in their home, if you do plan to get one sooner rather than later. Then, read AS MUCH AS YOU CAN and set everything up WELL in advance before you actually get any animal. You are correct that, possibly (and probably) your gecko didn't have the best start and perhaps that caused some health concerns. If/when you do get a snake, I suggest a breeder! You'll know it's healthy, and have it's background and papers. You can find adults from breeders as well, or at expos, so if you'd prefer a well-started sub/adult, I'd also go to them. Personally I think a rescue might not be the best for your first snake because you never know what kinds of issues you may encounter. Especially after your gecko, you'll want a snake that is in good shape!

I will tell you that I am a full time student in university, that also holds a job, volunteers, and has a social life (well, I try). Snakes are THE best pets for someone like me. Hands freakin' down. I go away for a week to visit my parents up north? NO big woop. Put two water dishes in the tank and go. Exams for 2 weeks? They don't miss me anyhow. Want some company? They (may) sit and watch a movie with me!

Every snake's personality is different. And I can almost guarantee you'll at least want more after one, even if you don't actually get another one (but you will)...

I think you'd do a great job just educate yourself, be prepared for the long haul, and make sure to talk to your parents, and respect their wants/house/rules/etc.

All the best!

P.S. Don't forget a thermostat.