I suggest you give Ahrefs a shot.
It's a really powerful tool, and have arguably more reliable data than most alternatives.
They have a great metric called "keyword difficulty" (KD for short).
The basic premise is that keyword competition is mostly based on the number and quality of links pointing to pages that already rank for a particular keyword.
Ahrefs data shows that links are (by far) the most impactful ranking factor for a page. Therefore, it makes sense to analyze the difficult of ranking for a particular keyword (the level of competition) based on the number and quality of links pointing to the current results for that keyword.
So you can search for some keywords in your niche, and checkout their KD scores. Then you can also use their "suggest keywords" functions to find similar keywords that you might also consider.
Spend some time finding new keywords, checking their KD, and taking notes.
Keep doing this until you have a collection of keywords that have reasonably competition. Anything with KD of 10 or less would be a good start.
As a general rule of thumb, the higher the KD the more links your page will need to rank on the first page.