About the games:

In all of the games you train to become a master weaponsmith. You make your weapons using ores collected in dungeons, etc. The mechanics for crafting have changed significantly from one game to the next but the end result is about the same, you make weapons that you can use.

The battle system is very Tales-like, except you only control one character: Yourself. But because this is a Summon Night game, you get one (yes, only one) summon beast partner. True to form, you can pick: there's always a robot, a male spirit (usually a devil), a female spirit (fairy/demon/catgirl), and some kind of cute thingamabob to round them out. Your partner is basically your magic; each summon beast has his/her own list of spells and levels. You have five slots to use in battle for weapon techs, spells and items, and to make the game more interesting you can only use magic/items a certain number of times in battle.

Dungeons are standard RPG style dungeons with random battles. In terms of interaction, there isn't much...you can whack barrels and boxes to find weaponsmithing items; later games introduce innovations such as TREES that can be whacked with a SPEAR, GRASS that can be whacked with a SWORD, STUMPS that can be whacked with an AX, STONES that can be whacked with DRILLS, and finally they ran out of ideas so they placed random TARGETS that you could hit with BOWS in the third game...

In the first game, there was only one huge dungeon with a hundred+ floors (I think there was a second minor area as part of the story, I don't recall--but it has been awhile). In the second and third the game starts to look more like a traditional action RPG with different areas.

If there's anything else you wanted to know go ahead and ask. I can't guarantee that I can answer your questions (sorry, my weaboo japanese sux). Alternately: tl;dr accepted. I just happen to really enjoy the games and thought I'd share.