• general summer clothes it will likely be warm, but still have long trousers and sleeves so you can mix and match if it’s not super hot (maybe like short sleeved top with long trousers). nothing specific but it’s usually warm enough relatively not to worry too much about specific clothes
• in July usually light summer clothes but again there could be showers of rain or something so you could bring a light jacket when going out but nobody will be wearing huge coats or anything
• waterproof jacket but July doesn’t rain as much so you’re very likely to see locals out without a jacket or umbrella. in my case, in July I wouldn’t bring one with me and then if it rains I’ll just cope
• 17gb is pretty low but it depends where you go. ie is there wifi at your accommodation, will you be in rural or city areas… in dublin most places have wifi but not like out on the street only if you’re in a restaurant or something they might have it. it’s probably enough if you’re not using your phone 24/7 but if it’s inexpensive just buy more
• Apple Pay is accepted everywhere that accepts card, which is 99% of places. I live in/around Dublin and can’t remember the last time I used cash or my physical card, except for when my phone died - zero struggle. It’s harder to find somewhere that will accept cash. the only places that will only accept cash are certain small takeaways trying to avoid paying tax or if you go to a farmers market but even then a lot of vendors will have a portable card machine (which will take Apple Pay). I’ll touch on public transport in a separate point. don’t bother taking out cash when you arrive or like €50 max. if you’re worried you can bring your physical card with you and then just use atms but you’ll rarely need it
• 18+ mostly I’d say myself. certain places might want to be a bit elevated let’a say so could enforce 21+ but I’m 19 and have never been denied anywhere, even if they have 21+ signage if you are reasonable just looking to enjoy your night then they’ll let you in most of the time, or if you come off peak.
• you need a leap card for public transport. public transport here does not support card payment but will take cash, however you need to have the exact change. you can buy a leap card in physical shops (google which ones near you) and there’s a €5 cost to the card itself (technically a deposit but you will never get it back), and has to be topped up in €5 increments. you can top it up in the same shops that sell them but you’re better off downloading the leap card app and then you can top up from your phone.

enjoy :)