Once you sort out how Icelandic numbers one through four / einn through fjórir work (at the very least, learn the masculine form used with counting), then dive into the other numbers.
I quite like this simple Icelandic counting YouTube video:
Furthermore, as Dr. Jennifer Wagner from ielanguages.com points out:
“The numbers hundrað, þúsund and miljón have set genders (neuter, neuter and feminine), so it is important to decline these as plural numbers when using any number after 1 (i.e. tvö þúsund). It is also important to use the correct gender of the numbers 1 – 4 with these numbers. To make matters worse there can be more than one form of a number in a larger number. For example, hús (house) is neuter. So to say 2031 houses you must use the correct form of 2, 1000 must be plural and 1 must be neuter as it qualifies the noun house. 2031 houses in Icelandic would be tvö þúsund þrjátíu og eitt hús.”
Confused yet? Don’t worry—you’re not alone. 😉 Keep practicing. I promise it gets (a bit) easier, even if it doesn’t feel like it now.
Gangi þér vel!