First of all, that situation sucks, I'm sorry. Here's my thoughts on this:
1) Block them all everywhere, and if they're still harassing you online then report it to the authorities. Take screenshots and try to have as much evidence as possible to back up your case
2) Go back to your roots and think about yourself. As long as you're a good person who lives to your own values, these people can only smear your reputation as much as people who don't know you/know the real you will believe, because everyone who meets you will know that they're not telling the truth.
3) Remind yourself that it's not your fault, and you're not to blame for their actions. Self-love and self-affirmation, not self-blame.
4) Some dating apps (such as Bumble) have settings for finding friends and making new connections. Bumble has a "bff" section and a "bizz" section, for friends and business connections respectively. This might be a way of expanding your network while being able to vet the people you meet, perhaps helping you to be a bit more trusting of them.
5) You talk about this group of people, but hopefully you still have a family support network outside of that. Make use of this if you possibly can, it can only be a good thing to have a group of people (hopefully) on your side and by your side.
6) Don't define yourself by your past with these people, or the smears that they're painting you as. If you internalise them, then they're winning. You're a better person, the same but free of those toxic people. Success is the best revenge.
7) One thing I always recommend to people who are untrusting of people: Get a pet if you don't have one (if you are in the right mindset/financial situation/environment to be able to care for it properly). They will provide you with a new source of love, give you a new meaning in your life, and will also maybe force you to be more social (almost everybody who is a good person loves animals). It'll also help you maintain a positive relationship absolutely not based on your reputation, just on you as a person.
Hope this helps!