Plasterboard fixings ?

[J4CKO]

Got to put some shelves up for my mother in law, I took all my stuff round to do them and after much indecision she settled on two walls that were plasterboard, I had run out of the fixings I bought years ago for plasterboard and I know she wants to put books on one of the shelves so will need some decent fixings.

Not bought any in a while so any suggestions for what the best ones are ?

Will have a look and see if I can find the stud in the wall so any suggestions on a gadget to find them, want to go prepared so only need one visit.

[J4CKO]

Just got these off Amazon,

https://www.amazon.co.uk/gp/product/B07J476MTV/ref...

Put the two shelves up and they are rock solid, thanks for all the advice.