I have submitted this in a forum but I thought I would submit this as a hint too because it has become very useful to me.
OK. I am on level 25 now and everyday for the past week I have been able to go up a level by doing these things, without cheating>>
1. Growing peppers in a high level neighbors garden patch.THIS IS THE MAIN THING EVERYONE SHOULD DO!
Get a neighbor that is on a very high level (50+) and find a garden patch. Then grow bell peppers or tomatoes for 30secs and keep doing that. The neighbor should have all the monuments completed that give bonuses and everytime you harvest a crop and get rewarded ( which is like 25-50% of the time) you will get 575xp and 675simoleons bonus! This so far is THE BEST TRICK I have found without resetting dates and downloading cheats.
2. Buy loads of magic mirrors and try to have as many sims living together.
4 sims can live together without dating and just by being best friends so get all you’re sims to become best friends by making them go clubbing and then get them all to live with each other. Then buy loads of magic mirrors and get them to stare at them. When sims are inspired and they are looking at the mirrors in ttheir own homes they get 117xp for 4mins of staring. Sims in another house get 106xp inspired and sims uninspired get 77xp.
3. Grow corn, carrots or watermelons with sims that are unoccupied.
Sims need to be working as much as possible and the more you make them work the more you get. Depending on how much you can do, get the sims that aren’t working or starring at mirrors to do gardening.I recommend corn every 20mins.
Good luck and I hope you reach you’re goals without wasting money on useless houses like I did before I realised 4 sims could live in a house together