Can he call non-Muslims to Islam with the little knowledge that he has?

Praise be to Allah.

There is nothing at all wrong with conveying what you know of the religion of Allaah to non-Muslims, as long as you are certain that it is correct, such as the basics that you mention, like the five pillars of Islam or the pillars of eemaan (faith). Indeed, this is probably obligatory upon you, as Allaah says (interpretation of the meaning): “Let there arise out of you a group of people inviting to all that is good (Islam), enjoining al-ma’roof (i.e., Islamic monotheism and all that Islam orders one to do) and forbidding al-munkar (polytheism and disbelief and all that Islam has forbidden). And it is they who are the successful.” [Aal ‘Imraan 3:104]

The Prophet (peace and blessings of Allaah be upon him) said: “Convey from me, even an aayah.” (Reported by al-Bukhaari). Ibn Hajar (may Allaah have mercy on him) said: He said in the hadeeth, “even an aayah”, meaning one aayah, as if he was saying that every listener should hasten to convey whatever aayaat he heard, even if it is only a few. Some of the Sahaabah set out to call their tribes to Islam when they had only a little knowledge that they had gained during the brief time they had sat with the Prophet (peace and blessings of Allaah be upon him). But even though their knowledge was so little, it was correct and was blessed, and because of their sincerity, Allaah benefitted others through it. Al-Tufayl ibn ‘Umar went from Makkah to his people Daws with the limited amount of knowledge that he had, then he came to the Prophet (peace and blessings of Allaah be upon him) in Madeenah accompanied by eighty families of Daws, all of whom had become Muslim, and among whom was Abu Hurayrah (may Allaah be pleased with him).

Know that some non-Muslims may become Muslim for the slightest reason and by hearing the briefest word said to them. Do not think that the knowledge you have is too little for the purposes of conveying the Message. “… invite them to your Lord. Verily! You indeed are on the (true) straight guidance.” [al-Hajj 22:67 – interpretation of the meaning].