Basically what you're wondering is whether it's a good idea to have more on with your bad trades than with your good trades. In other words, if the trade starts right out going your direction, you have no opportunity to "average down". Therefore you have fewer shares on with your successful trades. It's only with your unsuccessful trades, the ones that move against you, that you add to your position. Lousy idea in my opinion.
That said, I rarely put all of my position on at one time. The reason for this is that in my early days my attempts to pinpoint my entries resulted in missing trades. Therefore, I put part on, see how it goes. Sometimes I can put more on at a better price. Sometimes I add as it goes in my favor. Depends. But when I put part of a position that moves against me, and does all the wrong things, I just get out. I don't add to it trying to make something work.
I mostly trade futures (ES) by the way.
OldTrader