So much brilliant advice on here. It's extremely painful for some and others just click with no issues. In bf classes, they tell you that something is wrong if it hurts. Actually they're wrong, it can be painful while your nipples toughen up and get used to the sensation - so painful that I would hold my breath and count to 10 in the first 4 weeks. At times I would really want to just take her off because I was so uncomfortable but I took each day at a time and persevered. There was nothing wrong with her latch, no tongue tie, I just had to get used to it. It paid off and after 4-5 weeks, it just clicked and I am still feeling 9 months later and absolutely love it.
As many pps have said, if you are getting wet and dirty nappies, baby is getting what they need. I never felt full or empty, never leaked milk and couldn't tell when she was drinking and when she was just sucking which made me worry needlessly about supply. Everyone is different and you won't feel everything that others do.
Have a look at videos of a good latch while pregnant, I found them really useful to know what to do. Also, be aware of cluster feeding so you don't worry when it happens. Ignore all misconceptions such as sleeping through with formula - my ebf baby was sleeping 8 hour stretches at night by 8 weeks (if only she still did that now). Don't stress about how you are going to feed when out in the first few days, it really does get so much easier a few weeks down the line.
Have some lansinoh cream, breast pads and a couple of bras with clips ready from before (I found the ones in small/med/large were best until your supply is established in then can get measured once things settle down). As for other stuff, I found having lots of strappy vests with nursing clips and one special nursing top (for the earlier days) really helpful and a good feeding pillow invaluable but that's me. I wouldn't worry about spending money just yet, see how you go and get things as you need them.
Good luck 