Should you make an effort? It’s supposed to be a kibbud. Begging doesn’t seem very honorable! Every shul has protocols, if you have a question feel free to speak with the gabbai.
How often? This depends on size of shul
Why asks for names? The hope is you will give a donation, offering you the extended MiShebeirach is an added value to your aliyah, as all those names receive the blessings recited in the MiShebeirach.
Typical pledge? Depends on person $18 is usual minimum.
Why say matanah? Some people don’t feel like naming a dollar amount on Shabbos. Some are embarrassed to say $18 especially when they used to give $180. Some want to give $1,000 but don’t want everyone lining up on his door that night.
Glilah? Every shul has their own protocol ask your local gabbai.