Gloss and glossier is the same thing. It all comes down to methodology.. If the paint has had a week to dry then block sand it with 150 sandpaper to make scratches on the gloss finish. This allows the new coat of paint to stick its fingernails into the grooves and hold on to the surface.(so it does not peel-because it could not hold on...as it will not just lay there like a damp rag.)

Primer is used on raw unpainted wood - yours is painted so I assume the first coat was primer. If it was not then expect the whole 9 yards to peel off someday.

I do not know what you started with and your procedure so I can not advise any more than that.

Have painted about 3 coats onto a table of water based gloss and decided I want it glossier.

Can I paint straight over the top with water based enamel (I assume thats the glossiest I can get apart from oil based?) or do I have to put on a coat of primer?