I'm new still and here's what I've been doing:

1. Enter Nether - this gives me practice on villages, wood/stone early game, what to loot and what not, finding lava pools and building the portal, and if I find an immediate fortress, blaze practice, gold find/trade/protecting myself with no armor, etc. Sometimes I do this as a pure enter nether (no beds, no food) but most of the time I'm going in as if I'd try to complete it.

2. Full inventory - gives me something to do with flower forest and spruce village spawns. Pretty sure most people do this in flower forest, pretty sure I'll get the WR doing it in a spruce village one day... It's a good way not to feel bad when you reset and get a useless (dragon%) spawn.

3. Obtain item - agreed with the OP on this one. I put up a 13 second golden apple and was immediately addicted. Keeps your eyes fresh in a new world if you're thinking about it.

4. All wood logs - MUCH hard in 1.16.1 compared to old versions but if I spawn in a jungle near (dark oak or savanna) I immediately start thinking "if I get a good nether spawn" and making a run at it.

5. RSG Dragon% - keeps me motivated. I know this is the goal. Gotta work on it sometimes and do full runs.

6. Guardian% - I mean, you are on a deserted island with 1 tree. Quick reset or play it for 2 mins and reset? It's fun to try. :) Good adrenaline rush for slow times.

Interested in all minerals but what's the kick to this? Iron, gold & lapis in a shipwreck, diamond in a temple, drop down into a ravine's water and grab coal & redstone before making a quick portal and going to nether for quartz? That could definitely be fun.

Cake could also be fun, I guess ... not sure it's skill building but an interesting one in some scenarios.

Practice mod looks great - I use the one-cycle practice, of course, but could use that mod.