Okay, you seem knowledgable, and understanding of some of what has been shared with you.
Moodle specs for Moodle 3.2 were PHP 5.6.x. Since you think you are running PHP 7 with Moodle 3.2, maybe Hostgater was able to somehow get this working. This would raise a red flag to me. Do you know if Hostgater installed your Moodle with a one-step script product? If so, another big "red flag."
To learn a little more about Moodle, do you have a "sandbox." If not, consider getting one going. A sandbox running Moodle 3.9 might do you a lot more good at "optimizing" your school's Moodle than experimenting with Moodle 3.2 on a hosted server. Yet, any work with Moodle will be beneficial. The problem with Moodle 3.2 is that you are not going to get as much help here, since we gave up Moodle 3.2 around 4 years ago and might not remember. It's just not worth it for some of us (not all) to go back in history trying to help a person who we know, if they still with Moodle, will see the need to be current.
Relative to Opcache, I seem to recall some success running Opcache back on Moodle 3.2. Oops, but this was on my VPS, not a hosted server.
When I first began using Moodle around 10 years ago, I did it on a hosted server, just as you are trying to do. Within two year, But things changed around 6 years or so ago when it was still possible to run Moodle on a hosted server.
So here is another idea for you. Consider getting a VPS with a company, maybe Hostgator, that allows you to buy one or two months. On a per month basis, this might see a bit more expensive, but only commit yourself for one or two months of experimenting. Work with the latest version of Moodle, Moodle 3.9. Then, if you feel good, you can buy a longer-term VPS at a more attractive per month cost.
We don't know what your skill level is. Are you already proficient in Linux and servers? If so, you might be able to get a barebones VPS at a lower cost. If not, you might need to purchase an additional utility, like cPanel.
I don't work for any server company and am not doing an endorsement. In my own case, I use GoDaddy. In the U.S., you can buy a reasonable VPS, wth cPanel, for around $45. Times 2, $90. Consider asking your school for $90 out of its office supplies budget (or other budgets) for your two months of experimenting. This could be a small cost for the knowledge that you will gain. I don't know what you might eventually need (horsepower), but Ken, Usman, and others here can guide you much better than I. I run a small Moodle. This summer, I have only a total of 200 students in five courses. This is "teenie-weenie" compared to what Ken and Usman, for example, do.
Hope some of this is making sense to you.
