i am new wondering what sort of online activity is required to get credit for top 50% or top 25%?
More and better activity than the bottom 50% or bottom 75%.
Badges and Bravos and Solutions have some weight. But "loyalty" (being here longer) and "attendance" (being here often) and participation (contributing meaningful posts) also have some weight. Oracles and Mods do read through the forums every day, they know who's helping people and adding value to conversations vs who's just trying to parrot some free lazy money off their next phone bill. Nobody outside PM really knows the formula/algorithm, I suspect it's half automated and half based on "merit".
If you can contribute to the community most days of the week, for a reasonable amount of time, you should get into the top 50%. You will learn much along the way and the rewards will come. Be patient and enjoy time helping other community members.