If you don't want to spend too much time, stick with some coins with high market capital. If you want to be active traders, read forums/news and buy low sell high! Happy trading!
Yes it is true, because if you focused in some coin you can easily monitored the fluctuation of this coin in the market. For me I advise some newbie to focused for the meantime in trading because they were learn a lot of thing in this kind of job.
In addition for now they can't join in signature campaign so, it's better if they earned bitcoin now using trading instead of no income.