You should play Suikoden IV and V because they do fill in some details about the Scarlet Moon Empire. Not to mention Suikoden V finally explains the backstory of Georg Prime which Suikoden 2 only hinted at. Interesting to note, both the Island Nations and the Queendom of Falena were first mentioned in Suikoden II if you kept up with investigating all of your recruits.

Its also a very good idea to use a guide to collect the 108 stars in Suikoden I because the game is pretty devious about recruiting some of them. Pesmerga is always been a pain to get but Leon Silverburg, Clive, and Pahn are all Guide Dang Its.

I really dislike the Elf section of Suikoden I but at least it ended in a way you don't completely expect. Have I mentioned one of my favorite things about Suikoden Suikoden Elves spoileris that the series as a whole makes it a point to screw the elves over for being racist arrogant pricks? Seriously, it sucks being an elf in any game they show up in. Kwanda's section is one of two really cringe inducing sections of the game because Suikoden really played too many fantasy cliches straight and most of the non-human races in Suikoden I are assholes. Milich's section is also played more silly than it should have been, which is a shame cause some important things happen in it. Still, the first game may be really silly at times and certainly rough around the edges but I still have a fond place for it. One of those games I enjoyed before I became a pretentious "games are art" asshole I guess.

As for the Rune shards for weapons, except for Water Rune Shards, their are a finite amount of the other elements.

Water - Gives a Regen Effect that regenerates 5HP per Rune shard, add water element to Weapon
Lighting/Fire - Raise damage by a certain %, adds Fire/Lightning element to weapon
Earth - Raises Skill by 2, adds Wind element to weapon (you read that right)
Wind - Raises Defense by 3, add Earth Element to weapon.

Wind and Earth are glitched and somehow got their properties switched.

Stacking Lightning and Fire doesn't raise the effect, you should spread them around.

Earth Rune Pieces are supposedly dropped by the Boar enemies in the Gregminister region but I have never gotten them to drop so I'm not sure if their is a glitch preventing them from being obtained.

Water Rune pieces can be easily farmed and give some characters a much needed defensive boost (I like sticking it to Gremio's weapon personally) but sadly Water is kind of the weakest element to have on your weapon as not many enemies are weak to it.

Who is your party so far? Thoughts about Viktor and Flik's humble origins?