Should I launch an MVP and patent or copyright it and then look for funding or should I expose the idea to investors first?

Your best approach would be to file a provisional patent application - you can effectively do this yourself if you are able to write a meaningful disclosure, meaning, that the disclosure is clear as to what your program/system is, how it works, and what it achieves. The USPTO filing fee for a small entity is $130.00 or for a micro entity - $65.00. This will provide you with a one-year window in which you can arrange funding, find investors, see what the marketability or acceptability is for your program/system, and the like. At the end of the one year, you must then file either a US non-provisional application or a PCT application in order to perfect/convert your provisional application. If you do not do so within the one-year time frame, your provisional application expires and you will never receive a patent because provisional applications are never even examined. Filing of the provisional application simply provides you with a priority filing date so that if you subsequently disclose your program/system to third parties, they cannot obtain patent protection on the program/system because your provisional application filing date provides you with seniority whereby your provisional application will be prior art to their subsequently filed patent application(s).