I recommend Stewart Hart's PottyMill as a starter engine.
Made from stock metal – no castings. Inexpensive. I found it a good balance between simplicity and difficulty. Pushed my machine skills without frustration making it necessary to kick the cat or take to alcohol! Didn't find any errors in the plans, plenty of others have built it if you run into trouble, and Stewart himself is active on the forum.
Certain lucky chaps are workshop naturals. Their saws cut straight, taps never break, holes are always in the right place, perfect finish, and they never crash the saddle or cut a wrong thread. You might be one of them.
I'm not like that at all! As a clumsy novice I found it best to start simple and work up. Much practice, forum advice and cursing has made me the advanced bodger I am today. Although I can do good work, it takes forever and I regularly spoil lashings of metal on the way. Every time I do something I get a little bit better, it's just taking a decade or two longer than expected for me to reach exhibition standard!
Dave
Edited By SillyOldDuffer on 16/06/2019 11:31:49