What are the minimal requirements for successful gamification?
In short, I'd say the minimum requirement is to understand which behaviours you are influencing and why.

Before you consider which game techniques to use, consider the 'story' of the product/service. 

Each story includes:


Actor/s. Who are your targets?
These actors are motivated by something. This is what your game should leverage.
There is a goal. What are you/the actor trying to achieve. Help them progress towards the goal. Motivational factors / game techniques should encourage behaviours that move towards this goal and discourage behaviours that move away from it.
The actor begins in a context. Understanding the context gives you clues to opportunities and constraints.
The actor progresses through a journey (or arc). Mapping this journey helps you know when to employ certain techniques.
An outcome is achieved. This is the most critical part of course. 


Draw this out in a path. Include the diversions, obstacles etc. Identify the main path as well as the little loops of activity that contribute. 

Tip: If this isn't clear consider well known kid's stories. They are all shaped by this familiar pattern. 

The techniques you list above and ones you will see elsewhere are valid. However by considering the story you will understand when to use certain techniques and how they should be approached.