Gamescom is a massive event, bringing a lot of game developers, of every level and skill set. Unless something drastic happens to change my plans, 2017 will be my 6th year in Cologne.
I have a few more pieces of advice for you that I've learned over the years:
1. Look into Respawn and Devcom, the conferences that proceed and accompany Gamescom on the developer's side (bonus tip: volunteers are still needed, save some money on registration and be part of a community of like minded individuals.)
2. Tickets to the business area of Gamescom cost more, and you'll have to show you are connected to the industry (which isn't hard) but it would bring you access to people you would never see at the consumer area, such as sound engineering middleware companies.
3. That said, developer teams can be found at the consumer area, manning the booths on the games they worked on, whether it's from a small studio like Amplitude, to a giant like Ubisoft, so don't be afraid to go around and ask if there's someone to give you critique.
4. Don't go look for devs on the last day, though. The dates have been moved this year, but I suspect this will still remain true, as the show draws to an end, people will start packing up and returning to their day jobs, with only the community managers left behind to man the fort.
5. Act like you belong. They may be ladies, but trying to get past the women who sit at the entrances of the booths can be intimidating. Sometimes waltzing in like you belong is all you need to meeting some amazing people. Sometimes they will kick you out irately, but it doesn't hurt to try. Sometimes just looking interested in a booth will be enough to be invited in, usually with the smaller studios. Never know where that might lead. At the least to some cool swag.
Back to your original question, I think you GDC is still the one show you MUST attend, even if it is harder to get to, whether it's because of travel and living expenses to and at San Francisco, or because of visa issues (which as a Spaniard might not be as difficult for you as for others?)
GDC is massive, whereas the European conferences are smaller and split amongst the many countries with an established or emerging development community, and the ones in Asia are much more focused on the local market and without knowing the language, it will be much harder to communicate.
I think I prattled on long enough, but if I think of anything else, I'll write it down