Heyyy Echo... wow, Second Life is so vast and ever-expanding. You've got to take it day by day -- and even if you do, you'll likely be overwhelmed. But I mean that in a good way. Stuff forms and when you look back in hindsight, it'll make more sense. But eh, the craziness is a wonderful thing about Second Life.
I'm personally involved in a diversity of things. Many things interest me. I'm an explorer-class, so... here are some things I do:
-hang out in Welcome Area and see if anyone fascinating is around... maybe riding by on a vehicle. If you meet someone friendly who offers you a ride, go for it! You never know where the journey will go next
-check out sandboxes to see who's inventin' what. Crazy gadgets make me laugh so hard. I've got to meet some great people this way!
-check out the Top Picks tab, and through people who you get to know, check out their personal picks. One thing will lead to another -- it's what I call
existential sequencing. Even if you don't try very hard, if you have fun along the way, that's what ultimately matters!
-I pick a random area in the gridverse to travel to by just clicking wherever on the map, or I look for long tall lines of green dots to see what's hot and happenin' -- usually these are clubs and popular events.
-related, check out Events and attend the ones that interest you. You can make some great social connections this way and get to know cool people to hang out with!
-if it appeals to you, try your hand at some of the creative activities like building stuff... maybe you'll be working on something and someone else will come to ask you questions, and a beautiful friendship will develop! Who knows!
A warm welcome to you!

I hope to see ya inworld soon.