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I am a new to gravel bikes and a roadie , never really done mtb’s. Went out yesterday in Santini big tights and a Castelli Perfetto top with base layer. Seemed to work well enough but I’m not too keen on getting expensive jackets caked in mud every ride , so , i was wandering how everyone else dresses for those half road half muddy paths etc.
Same as I do on the road, dhb winter tights, MTB winter boots with gaiters, aldi winter jersey, endura gillet, decathlon winter gloves and no sense of style.

Is that on the way to see the school kids over the road, or the way home? And where do you keep your lollipop? 🤔🤣
a) Fit mudguards
b) If the good stuff is fragile and won't take washes wear cheap or old stuff. Just how often are you covering it in muck anyway?
c) Fit mudguards.
Just get touring cycling stuff from Decathlon
Check out the Endura stuff - MTR etc. They cover all needs and designed for the UK.
Stick an MTB rear mud guard on, you'll stay much drier as well.
Having holed a fancy rapha top on a bramble on my first gravel bike ride its cheap Altura and
Boardman in various sales for me. I do prefer roadie style clothing though and leave the baggies for the mtb.

Obviously you need proper gravel-specific stuff. I adorn myself with items carefully curated from the likes of Morvelo's Overland collection, Rapha's Explore kit and, erm, hits google, yeah, the Pactimo Gravel Grinding capsule collection. Erm, in my dreams / nightmares. In reality I use a mongrel selection of road and mountain biking stuff plus the odd bit of generic outdoor kit - Haglofs softshell shorts, Rab VR Alpine occasionally. I don't own much fragile, expensive kit, so it's not really an issue.
I don't really have a gravel bike either, just a beaten up old On One cross bike. I guess ultimately I just use whatever works in the conditions, though I wouldn't wear flappy, full-on mtb baggies, closer-fitting softshell shorts work fine. I guess I do fret about trashing my expensive Mavic winter tights, but it hasn't happened yet and they get occasional mountain bike use too.
I wouldn't recommend that hat Malvern Rider suggests. I found mine simply blew off at speed, though obviously YMMV. If you're going to wear crinolines, fit a skirt guard to the rear wheel. Sequins?

ps: you'll also need a beard as per TINAS, though a more minimal goatee will be more aero and save vital grammes.
As was said before - mudguards.
Otherwise I generally just wear the same kit I do when out on the mtb. Some liners (3/4 this time of year), good fitting baggies (Morvelo normally) and a base layer with jacket. For shoes I go with mtb xc style spds.
The downside of most mountain bike clothing is that it often doesn't have rear pockets and it feels wrong using a pack on a bike with drops, so I do tend to wear road-type tops and carry pump, tunes, water on the bike as per road, though I guess that's a personal choice.
Is that on the way to see the school kids over the road, or the way home?
I have the same gillet in black but Im more worried about being seen than being seen wearing head to toe black Rapha.
And where do you keep your lollipop? 🤔🤣
Ask your .........
eBay or classifieds. Buy decent used kit at cheap prices so you don't mind if it gets mashed.
and it feels wrong using a pack on a bike with drops,
The death penalty still applies in 47 US States for anyone found guilty of such a crime.
I wear road clothing and it just gets dirty. Only really a problem in winter months.
The downside of most mountain bike clothing is that it often doesn’t have rear pockets and it feels wrong using a pack on a bike with drops,
Missed opportunity for a quarter frame bag, more Gravel, obviously..
My gravel / cross rides tend to involve a pub stop towards the end. So baggy shorts are essential.
Gravel gear is like my youngest child. All the new expensive clothing goes towards my road riding. When road riding gets new stuff, the older stuff gets handed down to gravel riding.