Here's my current project. The entire time I am trying to avoid thinking about lighthouses, water, or anything of the sort. Especially when I am using a small brush. When I tweak the lighting/atmosphere at the end, then I'll allow myself.
Hope this isn't a spoiler, but I think you'll be pleased to find a very pretty lighthouse when you step back and look at your picture. A friend is taking some oil painting lessons. He got some good results, despite little experience. So I shopped for some oils, looking for cheap primary colors to start. The nearest I could find is a set of eight or so colors, in very tiny tubes. Is paint such a big expense?
It's not cheap, but a little paint goes a long way, and you can mix to get the range you want. You'll want some liquin and some linseed or walnut oil to mix with the paints to thin them and get different textures. I paint on plywood because I think canvass is a pain. We watched Tim's Vermeer last night. Really interesting. I have little doubt that Vermeer was doing something like that. It changes his art for me. Now I see it an amazing labor, but accessible.