You need to plan various phases of your product launch and allocate budget for each and every phase. As far as paid marketing is concerned, the budget for the same could only be decided after knowing your customer segment, geographical span, and your business concept. The cost of paid marketing varies to a great extent per above criterion.

Invest some time to review your launch vehicles with focus on integrated marketing strategy. Make sure you plan for 6 months to a years time to avoid getting caught unguarded down the line.

Meanwhile, have you worked out your estimated development cost? If no, then you should do that on priority.

As far as equity sharing is concerned, we had published a blog titled "Happy Equity Index" a while back. You can read the same to get further clarity around equity sharing dilemma. All you need to do is to type "Happy Equity Index, 366Pi" in Google's search bar.

Hope above helps!!