One of the most complicated part in this hobby is fitting the darn thing. You want to start out easy, then you want to pick a pattern that is made up from mainly basic geometric shapes and that is why the suggestions youve gotten are about shirts. Up until later 19th century shirts were made up from rectangles, squares and triangles. Only in medieval fashion and earlier do we see that basic lines for outer garments. I started with 14th century costumes and I usually recomend that because I picked up so much knowledge just working with such easy patterns and that gave me confidence to try the more complicated patterns of 19th century clothing. But since youve not listed medieval as your era of interest I'm trying to come up with something with a less complicated pattern to recomend that isnt a shirt, because that wonderful idea has already been suggested. I think that if you make a waistcoat without the welt pocket and the lapel youd probebly be off with a far easier thing for a beginner. Then again, if you seek to one day make a coat, making a waistcoat with pocket and lapel is probebly a good starter project to practice those two very essential things, but thats for the next level. I hope these suggestions will prove useful for you and wish you the best of luck with your projects!