I imagine that just like with body shape preferences and how they can vary amongst individuals, personal preferences for penis appearance will vary.
Just focus on obtaining what you like and what will give you confidence, or perhaps better is to focus on obtaining what your partners like.
If I had to just pull a number out though, I’d probably go with 5.5” MS-girth for being proportionately pleasing. I like to set goals that are within reach, and don’t feel like they’re far out of the realm of possibility.
I’m not certain of your current measurement, but maybe just set 1” increase on length, and .5” increase on girth as your initial goal, that can be realistic for a PE newbie.
Keep track of your base-girth too.
You could use some software tools, or fashion some models yourself, to get an idea of how different proportions look.
If you’re going for pleasing aesthetics, you may want to factor in your body size, and/or your partner’s body size. I like tall women, and while my penis may make me feel masculine around petite ladies, it can appear inadequate next to a giantess. Though appearance is certainly not everything and caring too much about that can make you unhappy for no good reason.
Study for your goals, be consistent, and you should see results. You may be skeptical, but believe that it’s possible. I went all in, I also avoided ejaculating to boost my libido and blood flow, and I believed every moment of work I put in was paying off, and my length measurement permanently increased month after month to the point I no longer had interest in gaining length anymore, and actually wanted to cease increasing it any further for fear I could no longer perform my favorite sensation of going balls-deep during sex.
When I 1st began, I don’t think I would have believed a time would ever come when I did not want my penis to get longer, but I reached my goal.