Breathable fabrics simply means that sweat can get out, thus avoiding the clammy feel, but when the garment is very wet it doesn't breath as well and condensation still occurs. Many people are quite willing to spend a lot on a jacket, but don't take over trousers. True they can be sweaty, but they can be a life saver in winter. And don't forget a hat and gloves. Consulting a map in wet, windy weather can be nightmare, but weatherproof and plastic laminated maps are a godsend.
Some people never stop for a picnic, but food and drink always tastes better on the hills.
But save some emergency rations for the end of the day. If venturing onto the high fells a Survival or Bivvy bag could save your life. Before you buy, try stuffing all your gear into it. You might need a bigger one than you think. You don't need to buy all the gear the first time out.