Have you considered hiring the services of an SEO marketer? Marketing on the internet is a broad approach, and if not done right it could bring very little results. What websites to advertise on depends on what you're advertising and also your target audience.
A friend of mine is a designer, and he finds that the best conversion rate is from IG.
This individual is a designer and deals with images, so they would almost certainly get more engagements on Instagram than on so many other websites, this approach may not work for some other service.
Any online communities you recommend where i can advertise web dev,web design and graphic design services ...?
For web development and design you can try upwork, Fiverr or some other platform that connects service providers to those that need their services, graphic design can work on Instagram; These are the ones I can remember of the top of my head, there would be more niche platforms for such services, you just need to know where to look.