I know all employers have to have a pension scheme, should I use that or opt out?
Depends on the pension, pay into it but at a minimum rate and they should offer you something decent theses days.
I opted for a low pension as I inherited enough to get a second property (small flat) which the rent covers the remaining mortgage and what I would pay in a higher pension goes on maintanence. For me this way seems logical as if I die my wife gets the flat, were as with a pension the money goes.
Build an ISA up, I wish I had done that sooner. If you have not already get a credit card and buy and pay back on time stuff you were going to buy anyway such as fuel or food, build up a good borrowing record so you have a nice clean credit file which shows your responsible with money.
Don’t lease a flash car unless you can afford it. I’ve seen so many mates struggle but have a flash car on the drive and worry if they lose tiger job the car still needs paying.
Add what you pay in tax to the cost if something you see. So if you see for an example something you want at £100 say to your self that means I need to earn £120 to buy it. This has been my biggest deterrent against impulse buying.
This advice is based on mistakes I’ve made or seen others make. Others may very well disagree