You’re probably looking at about 35kg max in it, which is the size of about 1.5 gravel sacks.
What kind of poxy wheelie bin do you have?
We’ve got a garden waste wheelie bin but the sticker expired and I’d since bought a trailer so it wasn’t being emptied and now just gets used to store and move soil/compost around the garden.
Depending on how strong you are it’s easy to at least half fill it with soil. Put a sleeper or something under the lip when you tip it over so it’s not flat otherwise you’ll never get much in.
The limitation is usually once you’ve got it upright it’s actually surprisingly hard to tip it over onto it’s wheels once it’s heavy.
I’d beg/steal/borrow a wheelbarrow, try freecycle or local facebook groups? But a wheelie bin will work.