A buddy of mine did this to his N-Line a while back. I was curious about this as well so he gave me in depth information on what it takes. You can find all the i30N parts here https://www.carparts-pros.com/
. The only parts that you need are the Moulding sides (87751S0000 and 87752S0000). You don't need to buy the clips and screws as it comes with it. That said, the cost of the parts is not the issue, its the side skirts themselves. Just a fair warning that if you purchase the i30n side skirts the clips are not just on the bottom of the side skirt but run along all across the sides. So when he got it he was surprised and shocked that it is not a retrofit to the N-Line despite the N-line (or GT sport) having the same body line and panel. Ultimately, he decided to go through with installing it because at that point he couldn't return it and he didn't want the $1000 to go to waste with car parts just sitting there.
There is no other way to fasten the side skirts securely (and safely) unless you drill holes into the side of the body panel/door sill of the car. So that is something you really need to consider if you don't mind the cost. Also, he was lucky enough to find an auto shop that wanted to do the work (and skilled enough to do it). He kept getting the run around from auto/body shops that refused to do it because of potential warranty issues so that might be another challenge as you might not find any shop that wants to handle that project. Another thing to note is, when he brought it into the shop they told him that they had to drill very specific holes. The clips will not hold in place if they drill basic circle holes. The shop is very skilled and he created notches on the edge so that it holds to clips in place better and at the same time makes it easier to remove. It takes a very specialized shop AND one willing to do it. So you want to make sure you have a place in mind that is willing to do it if you commit to buying them.
It can be done, and when it is done correctly it definitely looks very nice and completes the look of the car. But yes, there are a lot of challenges you're going to face so you need to be prepared for that. If you have any more questions about it let me know.
Side Note: You can purchase the i30N spoiler with the triangle brake light from the carparts-pros.com and that one is just plug and play. No issues and not difficult at all to do.