The reason why I'm talking to you about equipment is that I want to run through how you don't need all of this different equipment to do mastering or any music production.
What happens for me is I never change any of my equipment unless I find something phenomenal. I have certain compressors and EQs and things that I like to use in my desks. I don't want gaps in those desks, because I'm going to want to fill that with more equipment, which will make me want to try more things.
But that won't make me better at mastering. That's just going to make me have more equipment. What I try to do is never change the equipment that I have, only use that equipment in the best way possible to get the result that I need.
The only way you're going to get a good, mastered sound is by using the equipment you've got, knowing how they work, and using them every day to get familiar with all the different combinations of those flavours they produce. This will then give you the sound that you know, that you like, that you get a reputation for – that you build a client base on.
In the box, I have one compressor, limiter, and EQ that I go to, and five plugins that I use all the time. These don't change. I don't bring new ones in. Yes, I will try new stuff; you've seen me do lots of product reviews. But it's very different when I use that product when I'm mastering because I know the flavours and sounds that are going to sound best. To get the best out of what you have, stick with what you've got, get to know them and use them to the best of your ability. That way, everything else you are doing within music production will get much better and more refined.
Don't always be on the search for new things. Shiny Object Syndrome can still kick in and get you to lose discipline and focus. You shouldn't be too busy messing around with 20 different plugins all the time.
If you look at any of the prominent mastering engineers, they hardly have any equipment and plugins. They know the sound of those and how they combine. Do the same with what you've got.
Stop searching for new things, work with what you got.