Can somebody help me with a home-brew method to produce a 3-4% alcoholic beer from wheat or barely without much apparatus.
You are asking us to describe how to perform a process that encompasses everything in this stackexchange. The answer could possibly fill a shelf full of books.
Instead, let me to refer you to few sources that have already summarized this for you:
(1) How to Brew, by John Palmer, which is one of the recognized guides . The first edition is available for free online. Chapters 1 and 2 give you the basic process when starting with malt extract where fermentable sugars have been extracted for you, and then you will need to understand Chapters 14 through 18 to learn how to extract the fermentable sugars yourself from grains.
(2) Prior post on the cheapest way to start brewing, which will correlate closely with the least amount of equipment needed. You can consider the kit sold by Brooklyn Brew Shop as being the minimum you need to get started making a beer from grains, plus you will need a bottle capper and unused bottle caps (or you can use twist-off plastic bottles) and table sugar (sucrose) to bottle the beer.
(3) Review video on making beer from grains on a one-gallon scale by Brooklyn Brew Shop. There are many more videos on YouTube on this topic, and I can recommend the ones on Northern Brewer's YouTube channel.
As far as making your beer in the 3-4% alcohol by volume range, it comes down to extracting less fermentable sugar from the grains as @Denny_Conn suggests - use less grain, mash at a higher temperature, and/or use a less attenuative yeast. 3-4% is not uncommonly low for German wheat beers.