“Can you get braces if you have bad gums?”

It’s probably not a good idea to get braces if you have bad gums. However, at the age of 17, you can get your gums in great shape in just 2 weeks. If you go to a reputable dentist and get a cleaning, then brush and floss and rinse with Listerine twice a day, your gums should be in tiptop condition. Unless there is an underlying condition, or it’s been over a year since your last cleaning, this is all you need to do to keep your gums healthy and ready for braces. Of course, you have to continue this into the filter even while the braces are on.
Good luck and keep brushing.

Yes, but it's preferred to get gums healthy through oral hygiene treatment first.

Bad gums should be addressed regardless of braces or not! They could be due to bad oral hygiene or an underlying medical condition, but at 17, you should be able to get it under control!! If it's just a matter of brushing better, you may not want to have braces because bad brushing + braces could lead to discoloration of the teeth or even cavities all around the braces. Brush, brush, brush!!

Your first step would be to improve the health of your gums, you do not want to move teeth that have gum disease. That would worsen the health of your teeth. Your first step would be to see a regular dentist for a cleaning and go from there.