Well the exact requirements as I got from XSEED, which worked perfectly for me:

• Go to Iris' house in the evening to trigger the cut scene
  
• After the 15th of Spring, talk to Rosetta to learn about the Moondrop Flowers
• Plant the Moondrop Flowers outside Iris' house and grow them until they bloom to meet Iris.
• One week after you meet Iris, you'll have the 2nd dream sequence.
• Talk to Mist in the late morning when she's outside her home watering flowers.
• The next evening you'll have the 3rd dream sequence.
• Attempt to visit Iris at night once you have her friendship level high enough (it says level 20).  Can do this pretty easily by giving her one of the Moondrop Flowers you grew once each evening.  Anyway this should trigger a scene with a strange man that will end with unlocking the gate at the end of the Fin.

For Black Iris, just keep exploring the Snow Ruins.  You'll also need to have triggered a couple of automatic events on Whale Island so keep exploring there too.

SO...

Is there a trick or a tip to getting a girl to go on the date with you?

10 FP and 10 LP with her, have the wedding bouquet, the upstairs bedroom, big bed.

It's Tabatha but can't get love event to happen and Minerva has not moved in yet.

I'm using 120 flame axe and about 200def and magic

i wish i could but this game, but i can't right now, due to serious lack of funds.

oh well, hopefully i can find a good deal on it when i finally have some money.

Minerva not moving in yet is disturbing, as in my game she arrived in early Winter. Have you tried making nice with Bianca as well? That might play a role, although I'm not completely sure.

That's a lot more involved than I thought it would be...Still, thanks for that!

Sounds like you need to bump up your defense a bit more. What armors are you wearing?

You should find Minerva for the first time upstairs in the Inn once you get Tabatha's love level high enough.

Got held up in copy-editing so sorry for the delay, but the review is live here:
http://news.vgchartz.com/news.php?id=3341

I've also got a special treat coming up on Monday if you've been wanting this game but haven't picked it up yet!

:D my order just came in! I'm going to go pick it up now...

Sweet, thanks! Adding it (and a few reviews besides) to the OP now. And now you've got me intrigued

Glad to hear it! What do you think so far?

Many thanks to you!