Technical: Good knowledge of a typical web stack or mobile development or both
Non-tech: Not much, you have just to show that your are ambitious and somebody who gets things done (or finishs them)
With good technical knowledge you do not need connections. Just get familiar with a technology, you like build some nice private projects and apply/go to networking events.
Regarding tech: demand for iOS devs is always high, Anroid too and for the web stack I'd recommend either Python/Django or Node.js/Express which are both easy to learn
The startup ecosystem in Brazil is growing nicely. I would suggest you get some practical experience, working on your own projects or joining some others. Just build stuff, learn as much as possible. Non-technical people just need to do anything/everything else to make the business work.
Hope we can help you find a great startup in the future!
What skills (tech and non-technical) and connection do you think I must have to work in a early stage startup?