Which rod?

Hi,
I'm a novice. I fish trout. I'm very satisfied with this season's action.

The trout here go up to 20 lb. rainbows and 6-7 lb sea-run speckled.
River, stream, and a small lake fishing.

I have a rod (7/8) I bought at Walmart, and a Martin Mountain Brook reel.
I caught a 8-1/2 lb. rainbow yesterday, and I wonder about my rod.

I saw fishers using light rods this season, and I wonder which rod or rods
to buy for next year.

I want to buy a decent rod.
I'm 66 yrs old( I can't believe it!), so I don't expect more than 4 years
more fishing. (that means, I don't want to spend all my pension on a rod!)

If you can advise me, that would be splendid!
I knoe there's a lot of experience and expertise in this newsgroup.

Thanks,

-- Lionel