Is there a more efficient way to level up?

I’m still learning all the mechanics implemented after gen III, and even then I never really understood most pokemon mechanics.

I just beat the story-event after the 2nd gym and am at the crossroads. I’m playing on Normal-difficulty, no challenge mode, and the wild pokes and trainer pokes mostly seem to be outleveling me.

I have my Delta-Venusaur which is about level 44 (above the average I’m seeing). Everything else in my current team of 5 (including D-Venusaur) is 30-35 (Excadrill, Delta Gardevior, Azumerril (thick fat, unfortunately, but great nature/IVs), and Haunter).

In addition I have lower level pokes in my box which I want to level - but am unsure on the best way to do it. I’m talking like level 10-20 guys. I’d like to just drop them off on the daycare, but am afraid they will forget moves or never learn moves which I want them to have. Grinding them up to the 30/40 area seems like it would take a while.

So what are the effective ways to level pokes? I assume there are some tricks I’m not fully aware of.

Purchase this for your secret base and you should never have to worry about tedious grinding again:

As rocket said, the level trainer is a great option for grinding both pokemon and money. However, don’t be too concerned with being underlevel, since with a good team levels do not play a huge role in battles.