Dany,
I have bought many of the devices. Some work, but none do what they claim in their fancy advertisements. The best I ever got from any device, worn all day, was 1/8 inch a month. A far cry from the claims they make. You can indeed get that much from manual exercises, and save a lot of money. The manual exercises put a lot more pressure on the penis for shorter durations, and the equipment uses low pressure for longer times. Both seem effective, and the key to either is actually doing the exercise. Just forget about 1 inch in 3 months.
And you are not going to get significant gains from manual exercise if you stay with 30 minutes 5 day a week either. That is a good place to start, so your penis can get conditioned and you can perfect the exercises. But if you want real gains, you will have to invest real time. Some lucky few will get easy gains, sure - but most of us consider ourselves extremely fortunate to get an inch after a whole year of hard, daily work. In 5 years or so I have gained almost 2 inches. 5 years. But if I had not done the exercises it would still be 5 years later and I would now have a small dick instead of a big one!
"In an honest Service there is thin Commons, low Wages, and hard labour; in this (Piracy), Plenty and Society, Pleasure and Ease, Liberty and Power; and who would not balance Creditor on this side when all the Hazard that is run for it, at worst, is only a sour Look or two at choaking. No, A merry Life and a short one, shall be my Motto."--Bartholomew Roberts