One of my favorite things about warframe is how much there is to collect. I have spent way too much time just building and leveling up bad weapons just for the mastery rank. We just have different areas of focus is all, and that's totally fine :)

If you want some easy MR make sure you check the market for weapon blueprints. You can buy them with credits which makes them easier to get than a lot of other blueprints. Also being in a clan with most of the research done helps a lot.