Best grinding spots for the Lapis gym?

[ASadViola]

Hi, I'm having a lot of trouble dealing with Shelly, despite having a ground AND fire type (Onix and Growlithe), and I realise I'm pretty under levelled. Are there any good, quick grinding spots nearby that won't result in my pretty low health pokemon getting knocked out super quickly? Also, any trainers?

 

My team:

Lvl 32 Frogadier

Lvl 31 Emolga (Pretty much my main for this battle)

Lvl 28 Growlithe

Lvl 30 Roselia

Lvl 30 Krickertune

Lvl 30 Onix

Edited April 18, 2019 by ASadViola
Extra information for better advice.

[SilverAngelus]

You can battle the trainers as much times as you'd like in the Grand Hall~

Also, nice profile picture  

[Des Teto]

Also, the cave you just went in is a fine grinding spot at this point. There, you can catch a Geodude/Graveler just for this fight. Onix tends to lack power before evolving.

[ASadViola]

Oh, thank you! I didn't know about the re-battleable trainers in the Grand Hall! Are there others places that Growlithe could grind though? Since like, the cave is full of rock types that O-KO my underlevelled fire typed doggie.

[Orsan]

The mountain across Beryl Bridge blocked off with a Rock Smash rock has wild Ice-types to grind on.