It varies by person so you'll have to do the math based on how much you plan to play. Legos plus Lavas is a billion in resources and some people can do that in under 2 months, others 2+ years, and still others choose not to ever upgrade their walls to Lavas.
I was in a clan with a guy who did all legos start to finish in 18 days. I myself did them in a couple months, and just recently started grinding lavas (44/250 done so far). If you're a reasonably good farmer, you should be able to do 10-20 legos a day with boosts. I'd say 2-4 lavas a day with boosts as well. These numbers are accurate so long as you are prioritizing walls.
All varies for every person, but as mentioned above, heroes need to be prioritized. Farm DE and get gold/elixir as it comes. Heroes can help you farm walls, but walls can't help you farm heroes.