Rubbing is fairly common with lower end components and bikes....but not because they are low end, but rather because of their adjustment.

Take time and familiarlize yourself with the proper setup, installation and adjustment of your components. The Park Tool website is great for this purpose.

In general....very general statement....you should be able to operate in almost every cog through normal use without obtaining chain rub on your front derail. Lots of small conditions can affect rub in the outlier cogs that can happen even when everything is adjusted correctly.

In general when you say you have the setup you have and you are getting chain rub to some degree in all cogs then you most likely have an adjustment issue. If I were a betting man I would say that adjustment is mostly likely (85% or better) the cause.