I don't think you would even like to be on 1st gear all the time, no matter it's free area or a huge traffic in there. As I think 1st gear is usually used to pick the drive only, you can stay on 2nd gear any way with complete control. I think Asad has given good instructions about all the figures and situations.
Best of the things is true that you must be careful while driving...... but don't ever get worried about how you drive. As I am feeling that you are being so much worried which you really should not. Just concentrate on the situation you get on the road. Shifting gears is completely depends on you that how you feel to go on with a specific shift(already said in above posts), of course with applying the instructions which have been given above already.
And yes if you are really worried and can't get the better of it, then you can also practice in free areas or grounds first but I would say that try to find free roads instead of the grounds. Plus, don't fight with two things simultaneously as you are trying to "learn gear shifting/driving" at one side while having difficulties with "road traffic"... It's good that you try to grip on your drive and control first and then get in the traffic.
Now... don't think about which gear you should be driving on when in huge or low traffic. You will know that when you will have enough control on your drive.