This works really well as a faux "idle clicker game" and it was enjoyable for quite some time. Particularly, I liked being able to customise your character, the training minigames which were very fun skill games, the collectibles in the home, the Easter Eggs and the medals, and the semi-turn-based mechanics of the battles which was very interesting. Indeed, this is very very good for a Flash game. Nonetheless it could be better. Here are some suggestions:
1. The typical progression of the next more expensive weapon being stronger than the previous one was very vanilla, very characteristic of the idle clicker mechanic. It would have been preferable to have a choice of strong weapons so that all but one weapon fall by the wayside. I say take some inspiration from Fire Emblem and Pokémon, and implement their "one weapon more effective than the other" mechanic.
For example, Fire Emblem has the weapon triangle which goes like this:
Swords beats Axes
Axes beats Lances
Lances beat Swords
You could have used this instead of making "the strongest sword to beat them all" the last purchasable item. It requires no thinking at all to get to the very end and just use the same sword over and over again regardless of your opponent. You could include a weapon swapping mechanic in the arena, whereby if you see an opponent with an axe, and you're wielding a lance, you can decide to switch to a sword so you have an advantage.
I can see this playing into other enemies too. Like bows being more effective against birds and apples, but not very effective against enemies wearing armour. Poison not affecting those mushroom opponents, and being not very effective against opponents wearing steel. Fireballs could be very effective against armoured units and plant-based enemies, Ice magic would be very effective against flying enemies and also plant-based ones. There are many more I can think of, but I'll leave it there because I think you get the point.
2. Put a limit to the amount of skills and talents you can buy and/or equip. It's so easy to make your character invincible and just max out everything. If you limit the amount of equippable skills and talents this makes the gameplay a little more complex so players are not only relying on a single strategy to just plow through the game. They could swap abilities around to better suit their needs. This would fit in well with another suggestion I'm going to make (see #5).
3. Make the enemy characters smarter. All enemies were very boring. It was just kill this and kill that. Their attacks were all the same too. Even the boss characters! They don't use different spells, they don't get critical hits, they don't activate abilities, they don't get skills or talents, not even *SPOILERS* King Sir Scarow gets, and he's supposed to be the guy honing your skills! it's just headbutt over and over again! This doesn't make sense. He should at least be able to get a critical hit in. *SPOILERS* If you made the bosses much more remarkable it would have been better. All the battles are quite unremarkable. Even though I praised you on your interesting battle mechanic, all the opponents take almost no skill to beat especially if you've grinded up sufficiently. You should penalize players who just grind and overpower their characters without thinking.
4. Add a better story. What the hell is the point of battling in the arena? Are you just some dude who wants to kill a bunch of monsters? Why does the Scarecrow guy even take interest in you? Why are you so special? Aren't you just some stupid weakling? And if he's like the master trainer in all of the realm aren't there stronger warriors?
Heck even if it's just a generic good vs evil story. This game doesn't even develop plot regarding you and that woman in your house, nor does it explain why there are missing children everywhere. You don't really get anything from collecting all the missing children except for a trophy.
I think point #3 can also be added to this element. You can make the hero save the village from a dragon who collects rubies and diamonds, or maybe there are evil ravens stealing people's bags, or maybe a child-murderer in the loose who is super strong.
5. Add more "battle spots" that aren't the Arena. ALL of the battles take place in the arena. It would have been nice to have other places to go to, make them unlockables because this game got boring super quick. Maybe there are some dragons in the mountains? Or maybe a cave full of trolls? Sea enemies like sea serpents and pirates? There are soooo many options.
6. Improve the post-game! There's not much to do after you beat the final boss, save for continuing to play the minigames to try to beat your highscore and improve your stats, and playing in the Arena to fight never-ending opponents. After a while there's really just nothing to do anymore and improving your stats to ridiculous amounts becomes rather tedious and unrewarding, especially since the opponents don't really get genuinely harder. They're just a higher level, they don't become more complex, their attacks just do more damage. And if grinding is your game and that's what you find fun, that's good for you, but I prefer to be challenged in another way. The additional maps suggestion would be good for post-game, and maybe multi-player is a good idea too, especially if you implement all the other things i've previously mentioned. You could even include character classes. That would be great.
Anyway, in summary this is a fairly good game, but it's lacking in a lot of aspects. I'll give you a 4 anyway, because I think this deserves AT LEAST a 4 because it's a really good independent flash game. So with that said, if anyone bothered reading this review, yes I do recommend you play it despite all my criticisms. It's better than a lot of "idle clicker" games out there (even though this game really is nothing like an idle clicker). Have fun!