How serious is your macro requirements?
D40 is just above 1k with kit lens. If you can live with some loss of resolution and edge softness, close-up lens is a good bet, at least for beginner.
Don't get prosumer camera... That's the end of the road. DSLR is the beginning of a journey.
Step at a time, slowwwwlyyy. Get body, learn something and move slowly.
As for small viewfinder advise, hard luck. All affordable DSLR have small viewfinder.
Better bet is to get second hand D50/D70 to avoid limiting to AFS lens. First try macro mode on your kit lens if you buy one, then try close up lens, beg or borrow from friends. Then go for dedicated macro if they don't work well enough for you. Buy second hand...
There is also extension tubes, apochromatic closeup lens you can try.