Oracle have this very generous free tier for users that I really like honestly, but as we have seen every “free” thing have its con or limit. So now Oracle have started to stop(reclaim in their words) the servers which are just running freely and hogging up space and resources, I can actually see that its fair too since many times after deleting current instance I am not able to create new instance for couple of days and sometimes much longer than that for example previously I had account with Switzerland as a base location/Home Region and it was always filled fully.
For me its a deal breaker actually since I experiment too much and delete and relaunch server daily(lol on that) So I again switched to some paid providers.
Though Oracle now have started to reclaim the instances which are just running idle and have booked resources. this will probably force more people to use only the resources that are necessary.
So you have to find out what works for you.
they have stated their Minimum requirements to ‘NOT’ letting your instances be reclaimed HERE.
For me I use two servers for my account.
4 Cores are enough for me to have a small server and a remote desktop.
if you look at oracle’s minimum requirements, the remote desktop is not a problem. since it consume enough resources on itself to meet those.

Coming to server
- the easiest solution I found is running yabs.
adding a cronjob to run yabs script twice or thrice a day is actually more than enough.
* */12 * * * wget -qO- yabs.sh | bash > /dev/null 2>&1
This above cron will run yabs every 12 hours, and It will use enough resources to meet minimum requirements.
- Using Loader.io
Loader.io is website that lets you load your websites with thousands of clients at a time to load test it, and this is the method I have been using for myself, just a drawback is that you have to do that manually but after setting up its just a matter of one click and its done, you DO have to verify the domain to loadtest ofcourse.

Though loader.io will let you one minute test with whooping 10000 clients for free, so its a good way too.
you can see as the test was going on I used 4000 clients only for 20 seconds and it used good amount of bandwidth too, when I notched users and time to 8000 and 60 seconds and bandwidth went to much higher. but ofcourse it depend on webpage size too.