Safety wise you need to avoid:
second hand mattresses (everything else is fine 2nd hand)
pillows
soft toys in the cot
duvets (all three are suffocation risks)
Other than that- do what you want.
Some babies like to be swaddled (mine didn't). You can buy swaddling blankets or use a sheet.
You can also get baby sleeping bags
I went old school with sheets and cellular blankets.
You need to beware not to over heat the baby so I found light weight sheets and blankets the best as you can build up layers.
get a few as they piss, shit and vomit on them.
You can test if your baby is too hot by feeling the back of his neck. It should be warm but not clammy.
My other big tip is: don't buy fitted sheets for moses baskets. Pillow cases do the same job for a fraction of the cost.
Put the baby to sleep with his feet at the bottom of the cot, not his head at the top (iyswim). this will stop him slipping under the covers and suffocating.
Hope this helps :)