Let's Plays are a nice way to see the mechanics of the game. Other sources you could use are reviews of it, or good old Wikipedia.
Like Nick said,
Legend Of Mana is rather different from the other
Mana/
SD games. There is no predetermined storyline that you play through. Instead, you build the plot yourself, from building blocks you get by completing other building blocks. Some of them are places like your character's home, or the orchard (where you grow fruits and veggies). Some are towns where all sorts of colorful or cute characters live. And some are what you'd call 'dungeons' in most other RPGs (except that only some are actually underground). The order and pattern you place these blocks (called artifacts in the game) on the map determines some of the things that happen, or which enemies are a little stronger, or such things. Some artifacts can only be placed on or next to water because their stories require that. Usually, the further away you place an artifact from your main character's home (the first artifact), the stronger the monsters there will be.
There are lots and lots of things to discover or collect or combine. For example, you only pick a starting weapon for your character, but you can gain new weapon classes throughout the game. Each of those classes has a whole lot of different moves your character can learn. At some point, you gain a forge/workshop where you can use materials dropped by monsters and the fruits and veggies from your orchard and some other things to make new weapons with specific stats and abilities. Like Nick explained, pets can be gotten from eggs that you need to catch. After that though, the food you give the pet determines how its stats grow. Golems are similar in use to pets, but are created in a very different way. There are so many many details to this game that it requires several encyclopedias to describe everything. Fortunately, the game provides you with some books where information is added as you discover it.
Besides the placing of artifacts on the map and then visiting them, the game consists of talking to NPCs to gain new information and quests, and then visiting the dungeons to complete the quest. Usually, the NPC will come along with your main character on the quest and leave again afterwards. Other times you can pick your favorite NPC from several who are available most of the time. Your pet or golem always stays with you. Inside dungeons, gameplay is much like other
Mana games, except viewed a little more from the side than the top. The three of you (main character, NPC, and pet) walk around together, battling monsters and bosses. Dungeons are divided into parts that you could call 'screens'. That is, you can usually view most of that part on screen at once, with little scrolling.
The various quests and events combine to three main storylines focusing on related characters and events. There are many more smaller stories though. Overall, the game is about building a world with all these artifacts (building blocks), and at the end, fighting the Mana Tree/Goddess. I don't remember the explanation given for that last part very clearly, but it's not too important. Eventually you'll obtain an artifact containing the ending. When you visit that, you can end the game. There is nothing forcing you to do that though. You can keep revisiting other places and crafting new weapons and fruits and pets and whatnot.
Personally, I like this game a lot. Together with
SD3 it is my favorite
Mana game. Others don't like it so much though. Common complaints are that there are just too many unimportant details, that the game is too easy, or that the story doesn't make sense. Well, there are indeed tons of little details that you don't need to explore. They are just there for those who want to dig a little deeper. People who just rush through the game to the end will be disappointed. Or confused by all the things that don't impact the main storylines directly.
Legend Of Mana is a wonderful game for people who like to explore every corner of a game world and learn about the characters that live there. Those who are looking for a challenge, or who want things neatly ordered in sequence from beginning to end, won't like it as much.
Sheexy or Kassidy may explain better how this game compares to and influenced the rest of the
Mana series. There are of course many things it has in common with earlier games, most of all the general colorful and friendly style, and the various types of monsters and spirits. Some elements of
Legend were used again in
Sword Of Mana. That game is a remake of the very first
Mana game,
Final Fantasy Adventure, as concerns its story, but many circumstantial details come from
Legend Of Mana. The orchard for growing fruits and the crafting of weapons from materials for example are simplified versions of gameplay elements from
Legend. Li'l Cactus was so irresistible that it was added to
Sword as well. Nicolo is a familiar NPC from earlier games in the
Mana series, but his appearance as a sort of rabbit comes from
Legend.
The music of
Legend Of Mana was composed by Yoko Shimomura. Because the game was made for the PlayStation, it has a richer soundtrack than earlier games for the SNES. In addition to themes for some of the NPCs, there are themes for the various places in the game, and of course some awesome boss battle tracks. The opening/ending theme, "Song Of Mana" was sung by Annika Ljungberg, in Swedish (another reason why Squeenix should release this game in Europe; what's the sense of having a theme song in Swedish if the game isn't even available there?).
Well, I hope that covers most of your questions. Feel free to ask for more details
My German isn't too good, so don't think I can help with translation, but I could probably read what you write.