You may occasionally help them get a promotion or Skill up faster using a Potion, but that is about it.
Their buffs not lasting very long is the main problem, so their use is very situational. In most cases, unless you have a lot of Satisfaction saved up, the Emotion-specific Potions aren't worth it. Reward Potions are one-time use, but may be transferred between Sims by dragging from the Inventory to the other Sim. You can elect to delete them at any time, and should make heavy use of this, so that you can pursue Whims that are related to what you'll already be doing with that Sim. In short, the first Whim you see above the Sim's head is tied to emotional state and may change, while the other two are randomly generated based on what the Sim has been doing lately. The first article provides a lot of tips on saving and clearing Whims, along with how Whims are generated.
Getting Satisfaction is something you should pursue day-to-day by completing your Sim's Whims and pursuing their Aspiration. Satisfaction Points are the Sims 4's Lifetime Happiness, where Rewards are like the Sims 3's Lifetime Rewards. Rewards in Sims 4 Come in Two Types: Single-Use Potions and Permanent Traits The Sims 4 Rewards Traits List Store Satisfaction Costs and Reward Mechanics for Seasons Press 'G' then click the Present to open the Rewards Store
