1.) Don't be fooled by the very common advice of "Always do at least 1 science". Unless you seriously enjoyed jc science or really want to study medicine, there's a high chance you will have no need for any science subject. I do absolutely no science subjects and i'm looking at studying computers or data science in university, and even then there's no requirement for science. Very few courses actually require science and the science subjects sound like a hell of a lot of work.
2.) Don't do history. It is impossible. If you have an interest in history, still don't do it. I love history but i absolutely despise that course so i'm not going to take the exam. The exam layout SUCKS, you have to write 3 essays, each 5 pages in length, plus another question that has a 2 page mini essay. That's 17 pages in one exam. Even if you were good at the jc history course and those "People in history" essays that were there on the old course (dunno about the new course), the LC history exam is impossible and i highly advise you to just avoid it and learn history in your own time. You do not need LC history for any university course so don't waste your time.
3.) Do business, it's really really easy, like SERIOUSLY easy. Ok i'm bad at it because i haven't studied enough but it's still such an easy course and exam. Economics is also kinda easy but the research project in 6th year is really really stressful and the exam questions are harder to prepare for because there's more applying the knowledge, rather than business which is just very easily writing out memorised stuff without applying much knowledge.
4.) I'd say avoid practical subjects unless you know for certain that you are good at that subject. I know i wouldn't want to be spending my 6th year time on a practical project that i could easily mess up and waste a lot of time on.
look at courses that interest you, its really important that you dont rule anything out just because you "didnt know". If you want to keep options as open as possible then at least one sci and a third lang (if you do irish) are practically essential. Qualifax have a great tool, if there are subjects you know you do not even want to touch lol https://www.qualifax.ie/index.php?option=com_wrapper&view=wrapper&Itemid=26 of course the most important thing is do subjects you enjoy, that way they come naturally and exam wise, they can go a bit smoother. When we had to choose, I looked at some CAO options and the subjects i did good in for my 'junior' and they turned out to be subjects I really enjoyed. If you have the resources, take apptitude tests. they are a great bit of help if you have no idea at all. Do not let the teachers put you off, if you really hate the teacher just use it as motivation to be able to finish the course. Dont be scared to choose different subjects than your friends. If you 'enjoy' exams, choose subject that dont have different forms of sxamination like home ec has its practicals. or if you dont like 100% of the pressure on exams then definitely go for something like home ec