Hi, i'm trying to evolve a budew, but I heard it is evolved by happiness..

Give him a Soothe Bell which you can get from a lady in the Mansion on Route 212. Make it hold that and it's happiness will go up quicker

To make a Pokemon happy, you must use it a lot in battle. It also helps if you use items on it, especially healing items. Also, there is a little house in Veilstone City south of the Gym. There is a lady inside and she will give 1 of your Pokemon a massage every day and this increases your pokemons friendship.

You can always catch wild Roselia, but anyway...

Have your Budew hold the soothe bell, and give him berries that increase happiness but lower stat. Then, give him status uppers that correspond to the stat that was lowered. For example, if the berry lowered his HP, then use a HP Up. This will double his happiness rate, and with the soothe bell, quadruple it. Have him in your team, and NEVER deposit him until he evolves into a Roselia. Try using some rare candies, too. If you don't have any, he should still evolve in no time.

Vitamins, not letting it faint in battle, things like that. Or, the easy way would be, giving your Budew the Sooth Bell, from Route 213 in the Mansion I believe.

There are a few tricks to happiness. Battling is the most well known way. Items like protein and berries like the kelpsy berry also raise happiness. If you have A LOT of patience, walking MANY steps also raise happiness. A women in Veilstone City and a spa at the Resort Area (nationa dex + First visit, your lead pok� must have 10 ribbons) can also raise happiness. The Sooth Bell will also help in making the process quicker. If Budew was caught in a Luxuary ball, happiness will grow faster as well. That about covers it for happiness. After Budew shows 2 large hearts on the poketech, level him/her up a level and it should evolve.