> 2. start to read, use context to cover any weaknesses and gaps
> 3. become fluent reader, no longer need context to cover weaknesses and gaps.
That's completely not how you learn to read.
Step 2. is start to learn what sounds to make when you are seeing given combination of letters. And then learn gradually how to make the sounds faster and for longer sequences of letters. Until you reach step 3 where you can blurt a word or even few at a time as one or few sounds at good pace.
At no point the context comes into play. It usually is even harmful because it makes you make stuff up instead of reading. Often wrong, occasionally correct which seems even more harmful.
Context is important only after you read completely fluently and begin to read new domain of knowledg with completely unknow vocabulary. Then you can get some words meaning from context. Although you should always check if you guessed correctly.
If you would like to know more about how most people in the world learn to read please find out how kids learn to read in other languages than english. English is a bit quirky but in no way unique. What's unique is english approach to reading teaching. I don't think anywhere else kids are encouraged to make stuff up as they go.