You'll get loads of stuff for free or cheap on donedeal and adverts.
Some of it's sh/te, but some of it is good, too. When my brother bought his first house, he was of the opinion that it's his new house and it was only getting the best of everything. He bought all his electronics from a local shop, and furniture from a different local shop. Everything was financed. He spent a fortune. To his credit though, he never regretted it, and in fairness, it's about 15 years later and most of the stuff is still going strong (washing machine, bed, TV etc. all still grand, for example).
Though he did change the suite of furniture, and TV and a few other bits recently by choice.
Personally, I always hated the idea of adding debt to debt, but it's always an option if your mortgage will be inexpensive to you.
Personally, I reckon you'd need about 10k to get a nice finish inside a house. A grand will get you a decent bed/mattress. About a grand gets you a good sofa. I bought in Power City before and I got a fridge freezer, hob, oven, microwave and extractor fan (all integrated) for 1100 if i recall correctly. Kitchen will presumably be there already in the house for you. You'd get a decent TV for 500 euro.
You can spend a lot, of course, but if you're keeping your budget at the forefront of your mind, you can get away with a small budget if you keep an eye on what you're buying. Your budget will obviously need to go up if you're putting in new kitchen, floors, skirting, doors etc. but those wouldn't be a priority unless the ones already there are really in tatters.