I have two boys and I actually quite enjoy shopping for boys' clothes.
I have a rule of thumb now - look specifically for yellow, orange, green and purple. See what else comes up in between, especially for multipacks. (I find red and blue are overrepresented, white impractical, black just looks odd on babies - use sparingly) Get second hand bundles, weed out what I like, pass the rest on (charity shop/clothing donation bin). You end up with some grey/brown/blue from this but that's not a bad thing, because those colours tend to go well with brighter things so you can do a mix and match and not spend masses of money on the bright colours which are expensive - a few nicer pieces will do you for a whole age span. Whereas I think with girls' clothing I'd be overwhelmed by all the pretty patterns and forget to buy anything plainer to go with them and they would end up looking like a curtain factory explosion.
It can be fun to dig out the more exciting things from the mass of grey, brown and blue.
I do also have some girls' stuff for him - mainly trousers, a dark pink pair with dinosaurs on, light grey with rainbows, stars and hearts, a couple of bold flower patterns. Plus a couple of vests and sleepsuits that I meant to dye red and purple, which came out luminous pink. He pulls them off just fine, especially when put with a plain or "masculine" top (though the other day he had the dinosaur trousers on with the pink vest as a t-shirt and it looked lovely).
Cyclemad - try M&S, their toddler/baby multipacks work out well like that plus are really good quality for the price, and although they have a lot of naff character stuff, they also have plenty of plain. H&M for joggers and hoodies, Next for t-shirts and shorts. These seem to be the specific areas they do well at respectively. And I used to be a big fan of Boots' bamboo toddler socks, but I don't know if they're as good any more.