Evolutions are a big part of the game in the Pokémon franchise. They’re useful for combat, but also can be just kind of cool to look at. There are plenty of Trainers out there that want to capture all 493 Pokémon in Pokémon Brilliant Diamond and Shining Pearl, but it takes a lot of work. There’s no easy way to get all of the nearly 500 entries, unless you cheat and use somehting like the duplication exploit, of course.
Some evolutions are locked behind trades, while others are meant to work with Friendship. Friendship is basically a measure of how much you use that particular Pokémon. Budew is one of the more common Pokémon in the new remakes. This partilcar roster entry relies on getting Friendship to a certain level. Once you get it there, and gain a level, you can evolve Budew into Roselia in Pokémon Brilliant Diamond and Shining Pearl.
And when you want to evolve Budew into Roselia in Pokémon Brilliant Diamond and Shining Pearl you also need to do it at the right time. The window is between 10am to 7:59pm in your local time. Use the Pokétch Friendship meter to check the number of hearts on the Budew you’re trying to rank up. Time the level gain and a high friendship mark during that time, and the evolution should trigger.
Aside from unlocking some evolutions, Friendship also confers positive bonuses in battle. You get more likely crits, and even can survive otherwise lethal damage sometimes. Maxing this out on your core team is a good idea.
Evolving Kadabra into Alakazam works very much the same way. There are many other evolutions you can hunt for.
Evolution items are a big part of the game now, in this modern era of Pokémon. There are tons of evolution stones and other items you need to hunt for, like the Reaper Cloth. One of the items you need to find to get the 400+ Dex filled is the Protector. This evolution item is used for a specific evolution, Rhyperior. There are both stat-boosting and evolution items you might want. You could also be hunting for the Electrizer, which is useful for getting Electabuzz.
There are plenty of other ways to fill up the Dex, if you’re willing to get a little crafty.