thanks to all who replied.

imagine reading how to drive a car but once your in the car not knowing where everything is lol!

lr-fbneo-neocd

As its name suggests, that's a neocd emulator, meaning a neogeo cd emulator. Galaga is a Namco game from 1981, it doesn't run on neogeo, neither on cd. With the proper romset, you can play galaga on lr-fbneo (without "-neocd"), read the documentation.

mame-libretro only allows MAME cores

Sorry, can't resist: only libretro MAME cores, there still is the folder mame-advmame for that MAME-Core and I am not sure what other non-libretro-cores exist (optional/experimental/etc.) which may add to the list of folders ;> .?.

I've been through a lot of guides in this forum and others, your tube videos, google searches but I cant find the solution. its probably something simple and I need your guidense.

The simple reason is that you'll have to run a rom with the exact emulator (version) that it was built for. See @Darksavior's link for more about that.

Launching Galaga (lr-fbneo-neocd). reading the arcade guides I got the roms version 0.73 for mame2003.

Then why are you trying to run it with lr-fbneo-neocd instead of lr-mame2003?

every place I looked gave different location to place the mame roms so I've had them here: Arcade folder, fba folder and mame-libreto none worked.

On RetroPie, Roms for lr-mame2003 should go into arcade or mame-libetro. The only difference between those two is that arcade allows more arcade emulators to choose from, whereas mame-libretro only allows MAME cores (also, the former show up in an "Arcade" list in Emulation Station while the latter uses a "MAME" list).

Regardless of their location, the roms still have to match the chosen emulator.

edit: typo