[color:"orange"]But I guess that the game is made in a way so that it is possible to get throug one way or the other[/color]
Yes. It also helps that I was playing a warrior that game, and could neglect intelligence (as a mage you can not completely neglect strength, agility or constitution, so it is harder to balance your stat points). I could rely on equipment bonuses (or an occasional restoration potion) for my mana requirements (only used a handful of mage spells, mostly learned from spell books).
I was level 45 when I hit the gong to head to the wastelands. That was a high enough level (combined with good equipment) that I found the area fairly easy (most people hit the gong in the high thirties to mid forties. Even the end bosses didn't pose much of a problem.
Of the 60 gold charms I got in the wastelands, I bought half with gold I brought with me and got probably more than a quarter from enemy drops. The value of the loot gathered there was enough to buy the remaining charms (about 10 to 15, or so), but the quality wasn't spectacular. I did replace my sword with one slightly better, and there are a couple potentially good axes in the wastelands, but most of what I found wasn't close to what I already had (though I bought some nice leggings from the merchant there).
After you let Zandalor teleport you somewhere else and clear that area, he will give you a quest to gather some people together (also, you can get your teleporter stones back there). When you complete those quests and hit the gong in that new area to start a ceremony, you will be sent to the wastelands. Feel free to hit the gong before gathering everyone, but as you suspect, it is a one way trip once the ritual to become the Divine One is ready to start, so you need to finish everything else you wish to first (before that, your character will just make a comment when you click on the gong).
One of the people you need to get for Zandalor is an imp, who is hiding in the area the screenshot is for. Like a couple of the other people, you need to get the quest before being able to enter certain areas, or before someone will be at a certain location.