I can't seem to get this to work.
Creating a party, only partial options. Cannot go to 2nd character etc.
So I then used per-defined party and then the game went to black screen. Nothing happening except what I think is game-play music. No response to any controls. Just froze with a black screen.

Really not happy about this, as this is the one MM series I have yet to play.

I don't know about this particular game, I've mostly played only MM6. However, I'll try to help so it'll bump the topic up to the top. I know I've seen some discussion about MM9 sometimes, but usually about it seeming incomplete.

Anyway, have you tried the support pages for MM9? Here's the link:
https://support.gog.com/hc/en-us/categories/201400969?game=1207658978

It looks like there isn't anything specific for that game on its support page, just the general troubleshooting tips that are provided for all games. However, when contacting Support they typically point out those typical troubleshooting tips first and ask for you try them first. That's because there are so many possibilities and something might not have been tried yet, and going through the list yourself is faster than waiting in line, and might even work. So definitely go through the whole list first, it could save a little time. :-)

Anyway, just in case you didn't know about that support link and where to find it, I'll describe where I usually find it for a game.

In your account games library in the list of games you have purchased, click on any game. A large area will appear below that game and reveal the game files for downloading. Near the top of that downloads listing will be the title of that game in big letters, and below that a button labeled "More v", with the downward arrow indicating it is actually a menu button. Clicking on that button reveals many options one of which is "Support". That will be the link to the Support page for that specific game.

You'll probably notice that menu button also lists an option for the forum for the game, and so that is also one way to find the forum for any game you have purchased at GOG. But since you posted here perhaps you already knew that? :-)

MM9 cannot really be called a MM game--at least not in the same vein as MM6-8, unfortunately. It's much different in character from the other games, and, indeed, it seems more like another game entirely upon which they affixed the MM label in order to sell it--aside from being much different from MM6-8 it is woefully unfinished (near the end of 3do) and it often feels strangely empty at times. You cannot fly and lots of things are pared way down from their counterparts in MM6-8.

I seem to remember that you have to finish the first character in assigning points and a name, then with the mouse you left-click on the picture of the second character in the column of faces on the right, finish him, then click on the third picture on the right, etc. and so on until you have done all four characters--then click the big checkmark at the bottom to continue.

Thanks WaltC, I'll try that :-)

https://www.gog.com/forum/might_and_magic_series/might_magic_ix_fixes_all_in_one_place

dunno why that thread isn't stickied but it will probably fix your issues.

Actually, for me, clicking on the next character portrait never worked. But using numerical keys 1-4 to switch between the different characters worked fine.

For the black screen issue, I have seen a solution involving replacing one of the game DDLs decribed in other forum posts, but have not tried it yet myself...