At the school where I teach we have adopted the Texas Instruments TI-84 family of calculators as our chosen calculator and here are some resources produced to help students master its use.
I recommend the "TI-84 Plus CE" if you are buying a model from this calculator family.
It is very important that you have a copy of the TI-Connect software; aside from keeping your calculator up to date you can transfer datasets from your computer spreadsheet into your calculator. It also allows you to take screenshots from your calculator that you can include when documenting projects.
These sheets were updated in 2020 for the newer TI-84 CE calculator. If you would prefer the older versions then they are all bundled here.
General tips / hints
Statistics / probability
2. Descriptive statistics II (inc frequency table) (video)
5. Regression
6. Regression II (multiple lists) (video)
7. Regression III (scatter graph) (video)
Algebra / functions
1. Solving equations with a graph (video)
2. Solving equations using the table
3. Solving simultaneous equations graphically (video)
4. Solving linear simultaneous equations with PlySmlt2 (video)
5. Solving polynomials (inc quadratics) with PlySmlt2 (video)
6. Plotting curves: polynomials (video)
7. Plotting curves: asymptotes (video)