If you don't have a calculator already, you may want to get one that has a display that can show conventional "textbook" notation on multiple lines. The display will look something like this:
Two good options for calculators with textbook-style displays are the TI-36X Pro and the Casio fx-115ES PLUS. The TI-36x Pro is excellent and was recently available on Amazon for about $20 (the details should mention the "MathPrint" feature). The Casio fx-115ES PLUS is also very good and was going for about $16 (the details should mention "Natural Textbook Display"). Checking the details is helpful because many calculators have similar names but not all support textbook mode. The TI-30XS MultiView is also good but the TI-36X Pro is better at handling scientific notation and they are almost the same price at the moment.