Love the crystals!

As for the dapps, I like to think of them like skins. All three mentioned are built on top of hive. so when you post in 3speak, it will show up in peakd and hiveblog. There are several dapps, including games. You can check out a ranked list here https://hivedapps.com/
What's nice is they are all connected to your wallet so you can log in with the same hive key for each one.

3speak is unique because you need to sign up with an email first. Once you're signed in with email you can connect it to this hive account.

You can post from peakd clicking the pencil up top. there are also more features for smooth blog posting. Plus, your wallet page is much nicer on peakd! Oh, and their is a new chat feature on peakd too.

In case i am horrible at explaining, Leofinance (also a hive dapp) has a detailed beginner guide https://leopedia.io/hive/