I'm not an artist, but I find myself looking for similar tools for the limited graphics work that I need to do on occasion. Most Windows developers that I work with keep Paint.NET around as a free graphics tool with a rich extension library written by the community (to provide Photoshop-like functionality that is not delivered out of the box).
Wondering if Paint.NET would be useful for your needs, too, since you mention things like the Lasso tool and Paint Bucket.
(Download page, if you're interested: https://www.getpaint.net/download.html#download)