The best skincare regime is one that suits your skin type. This can change as you age and it's very common to change your routine over the years.
In general, I would say there is no "compulsory" skincare step except for good sunscreen. This protects your skin against harmful UV rays which cause pigmentation and collagen loss. Additionally, vitamin A and C skincare products can also be useful for collagen preservation and further UV protection.
The rest of the products such as cleansers, toners, serums and moisturizers would really depend on your skin type and may not all be necessary. Different skin types have different needs: oily skin types may require some skincare to control sebum production, dry skin types may need more moisture serums or essences, sensitive skin types may require anti-inflammatory skincare ingredients etc.
Hope this was useful and all the best in finding a suitable skincare routine!
