this is one of those games that is going to cause me to forget to sleep and eat...

^^^Dude, what are you talking about? Speak English!! What is this..."Sleep" and "eat" you speak of? Such a strange fellow...

Can you simply play this game by fighting in dungeons instead of farming on the field?.

....You may be looking at the wrong series.

And the wrong developer.

Naa I have Rune Frontier on DS, it's just that sometimes the farming gets boring so I want to finish this game by by fighting if it's possible

YOu can fight and not farm if you wish, but you'll have to do something to get money. The best way is farming when most of your areas are in prosperity. If you plant enough re-harvestable crops, you can make at least 30k a day. You can always fish, I suppose, but that would be even more 'boring' because you would have to fish half the day, then cook the fish to get any decent amount of money...

This is likely a dumb question - Where do I buy grass seeds? I seem to not be seeing them when I check the shops.

Mostly yes. You'll need to plant one field of flowers to advance the story, and getting the best equipment takes a lot of money (which is easiest to scrape up via farming/fishing), but apart from that there's no real particular need to farm.

That said, you'll find that adding that to your repertoire gives the game an added depth.

Erik sells them in his shop. Top shelf, second or third from the left, I believe.

errr its always the things right in front of me that I miss

Don't beat yourself over it too much: it's lodged in with a bunch of non-seed stuff, so it's easy to miss.