Warm-ups will really help you to get the best from your training (now and especially when you are stronger) because they will prep your body for the work sets to come and will help you avoid unnecessary injuries.
Surely it doesn't take long to do a quick warm up? Just do a few reps with each warm up set and don't worry too much about exact %ages. So if you are squatting with 315, do 1 set with 135, 1 set with 225 and then hit your top sets. Just load the bar up to your working set load in a few steps. That way you are only ever adding. There's no switching.
You only need to do warm ups like this for your heaviest compounds. I only do a single quick warm up set for other exercises once I have lifted my heaviest loads for squats, deads, bench or rows etc.