Is that info current? Lots of it seems old, and before old hunters came out. I don't get too much time to game so I just don't want to waste much if I can avoid it
It's "current" in the sense that it was true during the months following Old Hunters when I was doing NG+++ with one of my builds. If you include Old Hunters, the notion that you'll get good gems during the normal course of the game is even more true because there are some
sick gems in the DLC. The absolute best gems are still found in the Chalices, though, whether or not you're using the DLC.
You have to keep in mind that the damage gems increase by amount (like +30) or by percent (like +10%). I don't recall off the top of my head but I believe the elemental gems (Holy, Fire, Bleeding) work the same way. Percent gems are ideal for weapons that have high base damage (like Kirkhammer, Whirligig, Ludwig's Sword) and amount gems are ideal for fast, low-damage weapons (Blades of Mercy, Threaded Cane) that land a lot of hits. You can get more specific with "+Damage Vs Beast" or "+Blunt Damage" but again this will be highly dependent on your build.
Whether you're going for amount gems or percent gems, you still want your weapon to be as high level as you can, not just for the base damage but also for the additional gem slots. I forget the exact levels at which slots unlock, but you won't have access to all three slots until the weapon has been upgraded several levels.
I'll use Hunter Axe to illustrate: Axe goes from 98 Physical and D STR scaling at Level 0 to 196 Physical and B STR scaling at Level 10. That's a pretty significant leap in damage especially if the character has been pumping their STR stat. Yes, adding gems will make your weapon even more crazy-powerful but it won't compensate for an underlevelled weapon. Besides, pursuing the best gems will take
much more time than just upgrading your weapon. So, you might as well do that along the way.