Its easy to get wrapped up in it all and become a slave to the latest designs/technology/products that are thrown your way, but at the end of the day folk have been running on the fells for decades and decades and done just fine. As long as you ensure you are a) safe and b) comfortable, then all the rest will fall into place. Sounds like you've already covered most bases, although you should invest in a bag if you are looking at racing longer term. You'd be surprised at how much you can get in a bum bag!
I run with an OMM 3 litre bum bag, into which I can get waterproof top, bottoms, compass, whistle, few scraps of food, mobile, map and a smaller water bottle if needed. 3-4 litres is plenty. Longer runs I take out an OMM 'Last Drop' 10 litre race sack.
Just get out there and as long as you stay safe, you'll naturally refine (and sometimes customise!) your kit as you gain more experience on the fells. Everyone has different needs!