How to set up lookup from ground 0

Hi Guys, I am completely new to this type of database, only experience comes from excel/sheets, so forgive me for my basic question but none of the videos shows a true step by step for a simple lookup, and it is quite unclear what to link with what, I do not get results…

What I’d like to do is simple:

  1. Create a table with dfferent client Types with different unit prices.
    eg.
    Small
    Medium
    Large

and in a parallel column:
5
10
20
for unit prices.

  1. Creatw another table where client Types are listed ( not entered, but they are calculated based on an IF formula, that I managed to do based on their employee count)

  2. Assign unit prices to those client Types based on the first table.

Third one is my problem, no matter how I am trying to link stuff, no results appear, sometimes empty additional columns are added to either of the tables… Quite lost here, thank you for your support.

Br,
Daniel