Where you go next is entirely up to you and what your plans are. However, it's a good idea to start by running a system update first. Connect to the pi via ssh and run the following commands:
sudo apt-get update sudo apt-get upgrade
Both commands may take a while to complete. Raspbian Lite is a pretty minimal install, so your next steps are probably to install a bunch of packages. By running the above first, you will make sure to bring in the most up to date versions.
sudo raspi-config
This will bring up the main menu.
This is a good time to change the password to something other than the default.
You can also do other things like change the time zone, keyboard layout, hostname, etc.
Enable SPI and I2C
These are both used in a lot of projects but are disabled by default. It's a good idea to enable them now so you don't waste time later wondering why it's not working.
SPI
I2C
