Ospreys had been 13-11 down after Simone Ragusi's try and Jayden Hayward's boot cancelled out Walker's try, but fought back despite having Nicky Smith and then Webb sent to the sin bin.
And Gibbes was delighted with his side's battling spirit to grind out the result, despite putting in a less than vintage performance.
"We can't get carried away with ourselves just because of the bonus point," he told the Ospreys' official website.
"We can be so much better than we saw against Treviso. We know we have to be better.
"On another night we wouldn't have got away with it. If we perform to our capability then we know we are a decent team but we were some way off our capability.
"But I'm really pleased that we are coming away from here with five points, as Treviso are a very dangerous side when you play them here - as the Blues found out a couple of months back.
"They've pushed Leinster and Ulster all the way this season, so we have to be happy with the outcome.
"We'd dug ourselves into a real hole in the second half, we weren't playing particularly well and we weren't getting enough of the ball to do anything so it was a pretty difficult situation for us.
"So the way that we came together and sorted it out was crucial. It drew a positive reaction and we got what we came for in the end."
The win keeps Ospreys in touch with Glasgow Warriors at the GUINNESS PRO12 summit, after the Scots' 36-17 triumph at home to Cardiff Blues.
And with the Blues also next up for Ospreys, Gibbes insists his side are already focused on getting another vital win over their fierce rivals.
He added: "Everybody knows that we need to improve on this performance. We've got two weeks now before the Blues game, so we'll need to start all over again in training this week.
"It's important that we learn from this and bank the experience. It's going to be some occasion at the Millennium Stadium in two weeks and it's vital that we back up the wins in the last three games with a quality performance to keep the momentum with us.
"The Blues will be up for it, it's a derby match with a huge crowd, so we can't get distracted."
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