If this is your first time forging on Halo 5 or in general, then do I have the map for you! Octagon Prime is the map name, grab it off my profile, its an octagon that you can build off of. This base plate of a map will give you a foundation to learn the forge mode from, and give your first time map build an edge on the rest.
What do I do with the map?
The answer is right here. I have built 3 maps from this base plate that look stunning in comparison to the drab old generic Octagon map from the old times. Octa-Crater of Atom; OctaGreen Cove; Octa-Bermuda Triangle
These maps are built in under an hour (for a long time forger) and are completely scenic, so gameplay is no concern for you noobie.
Good Luck! And feel free to post your builds here, Id be happy to see your progress.