I'm happy enough to be sitting at mostly all silver at the minute, struggling with getting the 2 Nurburgrings though, GP and the big yin, but I'll get there.
On the controller myself. i think a wheel would improve my times, but 3/4/5 seconds worth I doubt. I've more to learn about how to drive before I close that gap.
I'm always the same though, on the daily race qualifying time trials, I'm always about 2 or 3 seconds a minute off the pace on the top tables.
Just a case of plugging away to get better over time. I'm only really 2 months into racing again, hadn't touched a console for about 6 years there till I decided to buy a ps4!

Once I've achieved all silver, I'll go back and start attempting golds, though it'll take me a while to tame the beast that is that Sauber!! Need to have a very light touch on the trigger in 1st and 2nd on that!
I would say to the OP though, if you think it's holding you back that much, why not just save up and buy a wheel?
Incidentally, I think the DLC has been great value, not sure exactly how much I've won, but I've just rattled 5million or so buying a raft of cars, loving that old skool Merc!

I had about a million or so before I bought the DLC yesterday. So decent enough value.