I think the best ways to add size, especially if one is starting out or more or less in the more novice stages...
-Stick with the big 5-7 compound exercises first and foremost, as they are the ones that a trsainee can use the most weight on to load the largest of the body's structures/muscles and create the best systemic changes both hormonal along with strength, fitness capacity and building all over mass.
- Eat "enough" good food from the main groups.
-Add weight to the bar when you can, (squats, leg presses, deadlifts, rows, benches OHP's_) weekly or bi weekly as possible #2 1/2 to #5 pounds adds up over a few months.
-Consistency and determination are some of the best attributes.
-5x5 style rep and set routines are good layouts that can be easy to follow.
After the main work is out of the way, then some iso work for say arms and abs can be done.
If one gets their main compound exercises up to where they are using say BW, or 1/1/2x, or 2X bw, while eating well, you should certainly be a good bit larger and of course a bit stronger as well. It will be up to the trainee to put in the effort and hard work.
IMO, if one wants to put an inch on their arms, the best way, is to to gain #20+ of muscle all over the body.