Since you mentioned no budget, I'm going to assume it might be hard for you to afford a new GPU, CPU, and MB and RAM if you upgrade to DDR4. So I would try the steps below first before buying any new hardware to make SURE it isn't just user neglect out of naivety. Plus, the 980 is still a pretty good GPU, and prices are really crazy from cryptocurrency mining right now.
The problems you're describing are usually due to first time PC users not knowing that boot times, browsers and, OS and program speed in general can slow down from things like an excessive cookie cache (browsers), too much data and/or fragmentation on your HDD, having too many startups that don't need to run at bootup, or even malware.
Browser
It is very quick and easy to clear browsing history in Chrome. You literally just open the tool tree in the very upper right corner (3 vertical dots icon), hover the cursor over More tools, then click Clear browsing data in the little window that opens. This will significantly speed up Chrome if you never clear browsing history. One way to keep cookies under control is to use Chrome Incognito mode, which does not retain cookies. In this mode you can still have Chrome save passwords, but you'll have to login each time, though that is much faster after getting non incognito Chrome to save the password first. As long as you have auto fill enabled in Chrome, which it is by default, logging in with Incognito mode will be just a couple clicks.
You should also make sure Chrome is up to date. You do this by clicking the 3 dot icon, highlighting Help, then clicking About Google Chrome. The page it opens will say if it's up to date, and if it's not, it will update itself. If for some reason it doesn't (rare), you can check the build version against the build version showing on the Chrome download page, and install the new build if necessary.
Bootup speed
On W10 you manage Startups with Task Manager's Startup page. Most programs don't need a startup running, so you can probably disable most in the list as startups. It doesn't mean you're disabling the program. This can significantly improve your bootup speed if you have tons of unnecessary startups enabled. You can also disable auto updates in most programs, as manually updating them is quite easy.
OS and program speed
ALL drives, including HDDs and SSDs, slow down in performance as you put more data on them. The performance can be even worse if you exceed MS' recommended free space guidelines on HDDs, which is 15%. That btw is 15% of the ACTUAL capacity, not the advertised. For instance 1TB HDDs are typically an actual 931MBs, vs 1024. 15% of 931 is 140MB, so that's how much free space you need to keep on a 1TB HDD. This is the amount of space required for proper defragmentation, for SSDs, this does not apply.
Which brings us to another way HDDs can decrease in performance. Think of fragmentation as clutter. Whenever files, games, etc, are installed, those files are not usually sorted well, especially in Windows. Apple is pretty good about their standards for installer software, but MS will license pretty much anyone's installer with little to no standards. This is why PC HDD files get so fragmented. So it's up to the user to periodically defragment the drives (SSDs don't need this, as they have TRIM). It's also healthier on your HDDs. If you let a HDD go without defragmenting it a long time, then do one massive defrag, it can take quite a toll on the drive.
Malware/Viruses
This is another thing that can slow PC performance, or even keep it from running at all in some cases. It's always good to have at least one or two security tools to prevent viruses, malware, trojans, and rootkits. I like Malwarebytes AntiMalware and AdwareCleaner, and even their free versions are pretty good. CCleaner is also a pretty good free registry cleaning tool, and recommended by a lot of sites that diagnose people's DxDiag logs.