My two cents' for what its worth.
Some observations regarding pumping:
First of all, I know two people who swear they have increased in size from pumping. Male One I have known since he started, around six or seven years ago. I can attest that he has, indeed, grown noticeably bigger in length and girth. He was big to start off with, and I remember when he bought the cylinders he took measured photos of his penis for later reference. He is Afro-Caribbean for the record.
Male Two: An acquintance in his 70s or early 80s, Caucasian. I met him at around the same time, perhaps seven years ago. In his case any increase in size is much harder to quantify since he says he has been pumping for more than 25 years. He has no reason to lie, and I believe him. The point is, his penis is huge, by any standards. I am not going to give any figures here, although Male One has what I would describe as a 'porn cock', Male Two is way beyond that size. His penis is in no way deformed or marked, it is uncircumsised, and quite simply the biggest cock I have ever seen. He has absolutely no trouble getting board-hard, and this thing is really something to behold. Given his age it is all the more fascinating. Now, he says he was always 'big', but he puts his present equine size down to pumping, pure and simple. Since I was not around 60 years ago to corroborate this, I can only take him at face value. Neither I, nor the two subjects described have any reason to push pumping or pumping products. I, in turn have no reason to doubt the authenticity of his insistence that pumping works to the spectacular degree that he displays - and he loves to display!
I have tried pumping, and I must confess to loving the feeling, and the look and heaviness of the cock after a couple of hours in the cylinder at low pressure. However, I have done it so rarely that any permanent increase would be impossible. As we are advised countless times in this forum, the secret is in sticking with it.
But I digress. Before I started rambling on, my intention was to reply to the OP's question. I read somewhere, I think here, that if one was targetting both an increase in length and girth, one should concentrate on the length first, as it is much harder to increase length after one has substantially increased girth. Could someone confirm this? I have toyed with the idea of buying an extender in another thread here, however I am aware that using one is in no way a pleasurable experience, unlike pumping. However, the results seem convincing, with subjects reporting measurable gains in length, and some increase in girth too as a bonus, from what I have read.