After the 1st Spouse visa you will need an extension. At this stage, after 2.5 years in the UK, you will need A2 level.
After that you could normally apply for a permanent visa, known as Indefinite Leave to Remain. This is where an even higher B1 level would be needed.
We also have a post on how many levels there are.
We also provide immigration training and CPD for lawyers and those preparing for OISC exam. We have classroom/livestream courses and online self-study courses, accredited by CPD Standards Office, ref 80001, and accepted by The OISC. Visit our OISC training courses.