I saw some spell on the site without much ingredients. Only involve some chanting or one or two items. Will this kind of spells really work or requires a higher level and experience of the spell caster?
The number of ingredients in a working does not matter, some people chose to use none.
They have as much power as you give them.
They are just a tool to be used as an extension of the Will.
It is the practitioner that holds the power.
Magick is accomplished with belief, desire, and directing the Will and your energy and intent.
Honestly, ingredient based spells don't really differ from verbal spells. Verbal spells just use more willpower, focus, concentration and energy to cast. Some verbal spells are stronger than ingredient spells, and vise versa. The only difference in them are the requirements.