It is truly pleasing to learn of someone who wishes to do science as well as art!
I would strongly recommend getting a Johnson-V filter. It is by far the most used photometric filter and although it is possible to emulate its results by taking images in several other filters at the same time, that process is really not recommended unless you have no choice. It requires more exposure time with complicated calibration and data reduction processes to give inferior results.
Until your filter arrives you can spend your time productively working through the data reduction process on whatever images you have to hand. The results will not be compatible with measurements made in standard pass bands but you will learn much about what needs to be done. There are all sorts of niggles that need to be dealt with, as I have learned the hard way.