How do I develop relations with Investment banking persons through LinkedIn?

I would recommend going to the local CFA society events and networking that way. However, if you are set on Linkedin, just message people for coffee as it is time efficient and less risk for someone to meet you. Also reach out to recruiters and cold call for some jobs  as well. You need to be able to sell yourself though. You’ll start gaining credibility as you pass the CFA level exams. Imagine meeting someone saying you wants to work at X bank and enrolled in the CFA program vs someone who has passed Level 2. Also make sure you can add value to working at the company and not just about you wanting a job. The best response is usually the less evasive way: meet for a coffee and have them tell you their experience and what steps you can take, opposed to saying can I have a job? I know someone who did this approach and 18 months later he got a call for an interview at a top tier firm.