Getting this game in the mail today, any missables/tricks I should know?

Missables:

http://www.gamefaqs.com/boards/942423-dragon-quest-v-hand-of-the-heavenly-bride/50624821

Fast money tricks: no, not really. There's a great casino exploit in DQ6, but not really one in 5.

Who should you marry? That's very subjective, and there have been as many topics debating that as stars in the sky. Deb is the most melee heavy, Nera is the most spell heavy, and Bianca splits the difference, but it really doesn't matter. If you're a 100% completionist, Deb comes with a unique starting weapon you can't get any other way, but the game does not keep an actual record of this, so if you choose a different wife, that weapon will be out of sight out of mind and won't effect your finished file if you don't let it worry you.
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Frazee is barking weirdly!

A little bit of extra clarification about that list of missable monsters in the topic I linked to: the first eight of them listed, through #36 Eyelasher, are all found during the first phase of the game, the childhood phase. That phase of the game is linear, and essentially forces you to progress from one area to the next, and you'll lose the ability to go to the places some of them are without warning. Boring Bug and Burr Baby are only in that very first cave, though you'd probably really need to try to not get 11 of each, so that's no problem.

The main ones to watch out for very carefully are the ones involving the winter palace, especially drackeema. Much later in the game you do return to faerie lea, but the winter palace has been replaced by a TNT board by then. Meanwhile, the Screwball Pitcher has a very bad encounter rate. It's around the Coburg field during childhood, but it'll be a few minutes of a grind hunt to find your 11. Chances are small you'll actually gets its drop, as it' s a 1/128 seed.

The seemingly arbitrary number of 11 is because that's the number at which the drop information automatically shows up in the Big Book of Beasts even if you don't have the drop, but the thing about that is you're well into the game before you can get the Book. You need to play through the first major scenario and boss battle of the young adulthood phase before you can get it, so the entirety of your childhood monster hunting will be hand counted.

I believe the rest of the ones in the list, which are all ocean monsters, disappear between Gen 2 young adulthood and the time when you have children, AKA gen 3, but I really don't remember for sure if they disappear earlier than that or not, so the best course would be to get your 11 of each as soon as you're able. Without spoiling anything specific, the delineation between gens 2 and 3 is very very clear, just like the one between gens 1 and 2, so you'll definitely know when each transition occurs.
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Frazee is barking weirdly!

Yeah, and one possible spinoff project I may do at some point in my completionism file is to figure all that out, what levels on what boards yield what possible monster ranges. It's probably easier to not encourage people to rely on that, but rather just to get them where and when they appear in progression of a playthrough.
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They get added to the total, you just can't recruit them even if they're recruitable elsewhere.
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Frazee is barking weirdly!