One place to start is the Universal Language Dictionary. ULD Version 2.7 is listed on the Frath Wiki. ULD Version 3 is available in Google Sheet form.
The Universal Language Dictionary is a list of concepts that can be represented as a word in a conlang. Each concept belongs to a category such as "Function words", "Clothing", and "Foodstuffs". Each concept also has a level between 0 and 3.
To design your course, you can sort these by level, and then sort each level by categories as you wish. Level 0 has only 30 words and it make sense to do them in this order:
- Function Word
The other categories have dozens of categories and 100-1000 words in them, so they take more work to sort, but at least it's a start.
You'll probably want to deviate from this pattern some. I'd want to introduce some nouns and greetings before I get into function terms. I'd also introduce food items as soon as I introduce the word eat.
You'll need to introduce some terms that aren't on the list, and of course other grammar. There's no word for "the" or "a" on the list because those are not considered universal.
Some background information can be found here. This includes the relevant license for version 2.7 of the ULD:
Copyright 1992-1995 by Richard K. Harrison. All rights reserved. Permission is hereby granted for unrestricted use of these files by any individual for his/her own pleasure, private research, personal communication, etc. Use of these files by any government agency, business entity, educational institution, or any other organization requires permission.
I would guess that other versions of it have similar permissions, but I can't guarantee it.