@LuxCo don't run, as Whew said you'll fuck your joints. Concentrate on gaining muscle mass and reducing fat. Do it through diet and weightlifting. If you want to do cardio then yes, cycling would be the way to do it. Technically speaking, 1 ½ hours is the maximum optimal time to be working out for. It depends on how much stuff you have to do, but go for between 45 minutes to 1 ½ hours.
As for only having light weights, you can still gain muscle. Just do more reps of the lighter weight. You will have to invest in more eventually though.
The biggest takeaway you should have, is that weightloss happens in the kitchen. You can't expect to lose much weight just from cardio. Our bodies are incredibly efficient, which means if you eat the same you're gonna have to cycle for hours.
Increase your protein, decrease your carbs. Try to have at least a 500 calorie deficit.
Also, when it comes to working out, go slowly at first. You wanna get the correct movement before you start adding difficulty. And if you just go flat out and lift as much as you can as many times as you can... you're not gonna be able to walk. You gotta ease into it so you don't give up out of the gate.
