The “Approb-” part of “Approbation” should remind you of the word “Approval”. Easy, isn’t it?
“Gargantuan” should remind you of a giant who gorges on a huge amount of food. Remember thus!
Someone suffering from abou-lomania is about to do something but then again decides against it. He/ she is just abou-t there but never quite there because of his/her indecisiveness.
The “-go-” part in Ergomania should remind you of someone who is always raring to go, someone who cannot sit still at one place but keep on going, keep on moving forward.
“Oniomania” should remind you of someone who is obsessed with owning things.
Livery rhymes with shivery. When one is shivery, it is apparent from their outward condition. Similarly, livery tells us about the rank and status of the person clad in that.
You assuage by providing assurances about a good future to an aged and weak person. Remember the word “Assuage” using the words “assurance” and “aged”.