For me, lowspend is about the 'cheap sheets, expensive pillowcases' Philosophy of Life - ie getting the best stuff out there for pence, and knowing what not to spend on.
So, for me personally, it's Primark trousers all the way because they fit and I rip the arse of all trousers (see below).
Jeans? ££ no object as I like a swanky label - by ££ no object, I mean grabbing Acne jeans in TK for 30 quid.
White tees - anything white, really - cheap because it don't stay white. Crisp white looks the best even if 99p Primark.
Bags - Flo here I beg to differ
. A decent bag can be cleaned pretty easily and lasts 5 years without going out of date, so if you like one (a big if) it's worth it.
IME it's only when you start cleaning a bag that you realise why it cost 1k - they come up like new.
I always worry I look like a homeless, doubtless correct given I tend to shoot out of the house in my volunteer clothes (nasty) with a fag on. Something about a nice Chloe bag redresses the balance, I feel.
Confidence can thus be purchased. My Stella McCartney bag was 14 quid in a chazza, btw. Buy the bag that carries you, not the other way round.
Underwear - annoying, this one, because it hasn't got so much sartorial appeal, but a decent bra and tights take a size off you every morning. Spanx tights cost £30 but would survive an ISIS attack and don't bag.
I secretly love pricy cashmere scarves - if you do, the charity shops take care of that hankering very nicely, usually for a quid.