Robbie Keane put the result of Saturday's Group D Euro 2016 qualifier in Dublin beyond doubt by scoring three goals inside 18 minutes.
Keane's hat-trick not only put the hosts in complete control but ensured the striker became the all-time leading scorer in UEFA European Championship qualifiers with 21 goals.
Ireland pulled further clear early in the second half, with James McClean twice finding the net and Wes Hoolahan also on target after Gibraltar goalkeeper Jordan Perez had put through his own goal.
O'Neill was delighted with the way his team took charge of the contest, but will now look to cut out the errors that crept into their performance ahead of Tuesday's clash with world champions Germany..
"We talked about it all week, about getting off to a good start, to get the momentum and impetus going very quickly," O'Neill told Sky Sports.
"It's really important for us, we are the home team so it is up to us to press forward and we did that.
"I was delighted we got the goals, that allowed us to settle down and in the second half that rush of goals just after half-time was terrific, [we were] just a little bit sloppy towards the end.
"The concentration is now totally on Germany."
Ireland have now won each of their opening two qualifiers, following last month's impressive success in Georgia, to the delight of captain Keane.
"We did exactly what we wanted to do," Keane told RTE.
"We said from the start, when we were in the huddle, that the most important thing was to get an early goal and put them on the back foot and we did that from the first minute and then the first goal settled everybody down."
An early goal would do wonders for Ireland when they face Germany in Gelsenkirchen.
Keane added: "We are certainly going to go there and give it a right go, no doubt about that.
"They might be world champions but we believe we can go there and get something."
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