Hello Hannu,
I would agree with the person swinging the club having the most effect. Having said that I think there is some validity in the idea that the parts having an effect on the whole. In my experience the ball has something to do with the shot. I still primarily play with balls that I find around the course. I've played with higher end balls (Pro V 1 and X, Nike Platinum Black, Bridgestone) and I found I was able to hold more greens using them rather than Top Flites or any other cheap ball. It probably has something to do with the hardness or softness but I feel that higher end balls give me more "feel". With the club face and head I am assuming you mean the type of head rather than the type of material or which grooves are used. I started playing with forged clubs (Wilson Staff circa 1984) so I didn't really know that there were clubs that were more forgiving. I still use Staff's (RM model) so I get a cavity back with the feel of a forged club. I really don't like the newer Calloway, Cleveland or Taylor Made clubs because of the width of the sole or the heavy top line. I think most of the "game improvement" club look clunky. If I were starting the game all over tomorrow I would probably choose a game improvement club if it helped improve my confidence. As far as a shaft I would agree with Low Post. I play with extra stiff shafts in my driver, irons but I have a slightly weaker flex in my hybrids. For me I tend to hook a regular flex shaft more. I would think finding a proper fitting club would be more important in making consistant shots. With the grip I would have to say that unless it is worn there probably aren't much differences in brand. I use a mid-size grip because they feel more like my softball bat handle. I would assume that a grip could be too small or too large but that would be an easy fix. The glove is a personal preference. I never wear one, I don't like the way they feel but for some they feel naked without one. That leaves the shoes. I don't own golf shoes, I should because I play some of my rounds in the early morning dew. I have literally spun completely out of a shot in my cross trainers. When I find a pair I like I will make a purchase.