If there's no wind and you hope to keep your catch smallish a 5 weight will suffice. I fished a 5 weight for a while when I just started off and it was so much fun on windless days.
I moved up to a 7/8 weight Elbe Pro Cast set up, I think the reel was an Okuma that looked exactly like the Diawa Lochmore.
Together it cost me about R 600-00. That was 10 years ago and I still use them.
The Elbe is cheap and can take serious knocks and keep going. And I don't know if this was just a sales pitch but I was told they used G.Loomis blanks for that specific rod. It handled very well in some serious wind and couls stilll lift a 2.5 leerie up from a 3 meter bridge.
Also remember that Grunter gets spooked very easy and long casts are needed and if therre is just a bit of wind you might really struggle with a 5 weight.
All that said, the best thing for you is to get out there and see for yourself. Experience it and make changes as you need to.
Brian