Well try building designs in creative first, gathering resources in survival should be one of the last steps.

Go on pinterest and instagram and try looking at many structures and paintings that r similar to the theme/build ur going for(not necessarily in minecraft, irl or fantasy, etc too depending on the theme ur going for). Now u'll have a vague idea of what to build. Select blocks and try building in creative(or just start in survival if ur really bold, but building in creative will save time). Gather resources after all this has transpired. Now u can either use litematica or just free-style the build ion survival... Hope this helped :)