Lightweight tool

Installing Jira on your own server doesn't require heavy investment in infrastructure. It can run reasonably well on a server with 2 GB RAM and a multicore CPU; of course, it also depends on the size of the instance. For small instances with a few thousand issues to big instances with millions of issues, the server specifications can vary and that is the great part of using Jira.

Atlassian recommends some specifications on this page based on the size of the instance:

https://confluence.atlassian.com/adminjiraserver/jira-applications-installation-requirements-938846826.html

If you're just getting started with a small instance then choose the specifications that are recommended by Atlassian in the preceding link. You aren't forced to set up a big infrastructure in the beginning.