Starting: How do I know if its battery or charger?

Evening chaps,

My new van doesn't like starting. How do I know if it just needs a new battery or whether its the starter or solenoid that's at fault?

The previous owner had it standing for several weeks without being used. When I turn the key it sluggishly tries to turn over but can't quite mange to. Easy to bump start though!

Question is in what order shall I try and sort this? Do I just charge the battery and see if it holds a charge?

Cheers!

If it bumps easy it's prob battery or maybe starter. Why not give it a charge first and see?

Sounds sensible!