I want to go niche because I have a bigger chance of converting sales, but since Portugal is such a small market I'm not sure if I'm not gonna be able to scale later on...
You are worrying about step 2 when you haven't done step 1 yet.
Cross the next bridge when you get to it.
Start with a small niche, don't even worry about scaling it yet.
And chances are, as long as you aren't selling low ticket items to a small niche, you can probably generate a lot more revenue than you may think.