Level 100 Statistics (see level 5, 50, 100)
Budew is a Pokemon that has not been blessed with very many good qualities; its attacking stats are quite low, and it is very physically frail. Budew's only redeeming qualities are access to Spikes and decent Special Defense, which give it a small niche to work with. It does sport useful resistances to Fighting-, Electric-, and Water-type moves, which do give it a few opportunities to switch in. Overall, however, Budew is quite weak, and if not used for its very specific qualities, another Pokemon is certainly preferred in its place on a team.
Budew reaches 23 HP and 21 Special Defense when holding an Eviolite, which is usually enough to set up multiple layers of Spikes. Giga Drain provides Budew with damage as well as modest healing, which is the perfect combination for this set. Sludge Bomb provides extra power, but lacks the healing that Giga Drain provides. Finally, Rest is a more potent form of healing for Budew to use, and the turns that would be spent sleeping can be avoided by switching out thanks to its ability, Natural Cure.
Team Options & Additional Comments >>>
Budew does have a few other interesting options to consider. A Life Orb or Choice Specs set could work with paralysis support, but many other Pokemon outclass Budew at such a role. Hidden Power Psychic is useful to do a bit of damage to Poison-types such as Tentacool, though it fails to KO most. Shadow Ball hits Gastly and Duskull, which is quite helpful at times. Hidden Power Fire's main use is to hit Ferroseed, but it has little utility otherwise. Sleep Powder is a great status move, but it is illegal with Spikes. While GrassWhistle is legal with Spikes, it is far too inaccurate to be worth the moveslot. Leaf Storm and Extrasensory are other attacking moves, but both are illegal with Spikes as well. Lastly, Swords Dance could work with Seed Bomb and Return on a Trick Room team, but Budew's low Attack stat means that it is entirely outclassed.
Checks and Counters
Tentacool is probably the best counter to Budew, as it can take any attack quite easily and has Rapid Spin to get rid of any Spikes that are set up. Flying-types avoid Spikes, and most of them can land an OHKO on Budew. Fire-types such as Houndour and Ponyta deal massive damage to Budew. Grimer walls Budew, though it can't prevent Spikes from being set up.