Wake turbulence: crossing under a final approach path VFR
Due to the nature of wake turbulence descending over time and weakening as time goes on, I would say that it's possible that you hit the wake of the 737, and just managed to avoid the A380's wake out of luck. It also depends on the wind direction as to the path of the wake, so it's hard to say in your specific case

Skybrary describes crossing wake turbulence as: 


  A cross-track encounter en route is likely to lead to only one or two sharp 'jolts' as the vortices are crossed. 


Which leads to me to believe you hit their wake, and not just some other form of turbulence.

In terms of wake avoidance the FAA says in 7.3.7(b).9: 


  En route VFR (thousand-foot altitude plus 500 feet). Avoid flight below and behind a large aircraft's path. If a larger aircraft is observed above on the same track (meeting or overtaking) adjust your position laterally, preferably upwind.


And skybrary recommends:


  In the case of crossing tracks, it has been found that the time interval necessary to avoid creating a wake vortex hazard is 3 minutes. 


In terms of a direction to cross the vortexes at this section of FAA 7.3.3(b).1 implies that you should do as you did and cross perpendicular to the path - as to avoid strong induced rolls:


  During inflight testing, aircraft intentionally flew directly up trailing vortex cores of larger aircraft. These tests demonstrated that the ability of aircraft to counteract the roll imposed by wake vortex depends primarily on the wingspan and counter-control responsiveness of the encountering aircraft. These tests also demonstrated the difficulty of an aircraft to remain within a wake vortex. The natural tendency is for the circulation to eject aircraft from the vortex.


To summarise those points in terms of enroute wake avoidance, and effect limitation:


Fly above their path
Position yourself upwind away from the wake path
Try to be at least 3 minutes behind the aircraft when crossing the path
And cross perpendicular to the wake path, to avoid inducing a roll


Sources: https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap7_section_3.html
https://www.skybrary.aero/index.php/En-route_Wake_Vortex_Hazard