Gama is a great shounen protagonist. He's straightforward and fun to root for, and best of all he's serious; he doesn't act like a cute but retarded toddler, or an arrogant angsty teenager, or a 40-year-old skeezeball, which is more than I can say for most shounen heroes. The shounen hero archetype doesn't need a surprising, deep human character to succeed. You don't need a human at all. They're almost always combat geniuses who eat a lot and never give up; the supporting characters are supposed to be the fun, dynamic people with unusual traits.
Gamaran flies light with very few supporting characters. I think this was a measured gamble and it pays off for the author. This is a shounen reduced to its skeleton, a shounen that immediately sets up its main character and his sidekick/boss and then puts them through a tournament-style fight sequence without any breaks.
The character and environment art is quite appealing. The biggest weakness is that many of the characters look very similar to one another.
The realistic setting is a serious challenge for shounen artists - they're depicting a real archaic age where people often wore similar clothes and cut their hair in specific patterns, so they've got to go above and beyond to make people look distinctive, and unfortunately the author achieves that only sparingly. This is yet another series that would've been well served by throwing in some more women. The endless sausage party in shapeless robes really strains the author's ability to come up with unique looks. After the first few chapters, you've seen "long-haired pretty guy", "tall butch guy", and "weaselly guy", and these looks will just keep coming back again and again and again. I'm surprised that I didn't see the shounen classic, "rotund guy". Everyone has a pretty average build.
A secondary weakness of the art is in depicting blood. Characters are frequently cut, but it rarely feels visceral or naturalistic. Blood drips down things in a paper thin strip; it doesn't have any solidity or fluidity, it's more like a painted line that appears on top of people midway through a fight. Characters often completely ignore wounds in a way that feels less tough and more like they weren't really hurt at all. This is a common problem in shounen, and it creates fights where the hits don't have real impacts. Gamaran's best fights are when people lose the ability to use their limbs; it feels like they're actually sustaining damage and have to build a strategy around it. The author seemed to realize this, and the hero is often partially disabled by grievous injuries. This was a brilliant move; it's much better to see shounen heroes overcome weakness in their own bodies, not merely strength in others. That's the benefit of having a so-called "generic" hero - we already know they'll summon the determination to fight and survive; the interesting part is how can they possibly achieve it?
Unfortunately, the villains frequently fall victim to "Shounen Villain Ego Syndrome" where they could definitely win if they fought carefully, but since they're villains they'd rather be cruel and overconfident, ruining their advantage or giving their opponents openings. Some shounen series acknowledge this and find a way to make it feel fresh. Gamaran does not. You almost feel bad for some of these guys, who'd be winning handily if only they weren't so easily insulted.
Overall, Gamaran doesn't have a lot of standout moments, but oddly enough I found myself reading it far past when I thought I would give up. Every time I thought I was done, I decided to keep reading. I think its greatest skill is being "not annoying". It's not distastefully perverted, it's not insultingly stupid, it doesn't waste time with putrid mishandled drama, it's just an honest, barebones shounen with a shitload of fights. After years of reading awful comics made by maniacs, I'm satisfied with a series that doesn't put its socks on after its shoes.
For shounen fans: I recommend at least checking it out for the first couple of fights. Don't feel obliged to read it too carefully; the author doesn't do subtle details or long-term foreshadowing. If it doesn't grab you, don't feel bad about not continuing. But if you like shounen swordfights... This series works, plain and simple!