I thought I would have problems with a boy as with Charlotte we got away with alot under skirts and dresses, but actually it hasn't been a problem at all. I find any brand of dungarees are great (apart from M&Co who seem to be very short in the body and long in the leg
) and I like Ben in dungarees. Other than that we have gone for stretchy trousers or sized up with jeans and turned up the legs - at this age it doesn't matter.
I think it helps this time that Ben is in pockets as Charlotte wore 2 parters which are bulkier, especially around the hips and they tend to come lower down the legs.
Ben's clothing has so far always lasted beyond the age range, he is still wearing some 3-6m stuff approaching 9 months. Vest extenders are a god send and we are using longies and t-shirts rather than sleepsuits.
I love Cut 4 Cloth trousers as they are a great fit, but as pp's have said, buy in the sale and they have a really good resale value.
It does of course make a huge difference and everyone has found that once their child pt'd they didn't have anything to hold their trousers up anymore!
But you will get used to what works and what doesn't and tbh I think every baby is such different shapes that everyone will find some clothes don't fit, even sposie wearers.
Incidentally I have some great trousers from Primark that Charlotte has been wearing for aaaaaages, they are 18-24m, I got them before she was 18m and she is still wearing them now at 2 years 9m! But there is probably a huge range of quality in Primark