Yes. It's subjective. Depend on your system and usage style.
Processors are probably the broadest topic in your question regarding the nuances of their performance differences and properties, but I'd say that as long as it has 4 cores or has 4 threads (i.e. the i3, which has two physical cores that have two threads each, effectively making it a 4 core processor), has a max non-turbo clock speed of 2.7+ GHz, and was released no more than 3 years ago, you should be able to handle almost anything with respectable performance. (That's a rough guideline, some CPUs might not meet all of these criterion but still would be good).
Adding more RAM can make a huge difference in the performance of a system, but that's only when there wasn't enough for your uses beforehand. When it's in sufficient supply, there is no noticeable performance difference. The bare minimum for a Windows OS these days is generally considered to be 4GB. 6-8GB is better and generally considered to be the baseline for any decent gaming system. If you're a power user who has a ton of tabs open all the time on a browser and/or regularly runs multiple programs at the same time that can use in excess of a say, 700MB alone, then 12-16+ would be great. Few genuinely need more than 16GB. I would say that for what I can gather from you, if you've got 6-8GB, you're set.
If you've fufilled both of the requirements above, upgrade the GPU.
$200 is enough to buy a decent mid-range GPU that can handle high settings on 1080p in almost all titles. Currently, I'd say that you'd be getting the best bang out of the buck if you get either a R9 270X (~$160) or a R9 280 (~$200). AMD tends to be cheaper than Nvidia.
If your machine doesn't meet two or more of these requirements, I would start with the GPU, then RAM, then CPU, but I'd like to know more about your system specs then to decide what to do.