In terms of wildlife, you wouldn't be using flash as your subjects would be very far away.
I would recommended starting with a single light. Perhaps the 430 EX-RT III. Do note though that if wanting radio control, there may be issues with dropped signals. In the past couple years, I've experienced that myself with 600 EX-RT units along with the ST-E3-RT trigger. Though when first starting with them in 2014 to up around 2021 or so, no issues at all.
Wedding can get tricky as you don't want to be firing off flashes at or near full power so as to interrupt the guests. You'll typically want to work with wider apertures and higher ISO values to allow you to use the flashes at lower power levels.
Family portraits would be the easiest, though will depend upon how many will be in the photo. Large groups would require a very large area to work in if using a single light. Or enough room to set up two lights. For the single light case, if it's too close to one side of your group, due to faster light falloff, the other side of the group will not be lit well.
In terms of modifiers, I would recommend starting out with an umbrella. Though choose a brand that would have accessories. e.g. the ability to add a diffusion panel to effectively turn the umbrella in to a large softbox.
Finally though, do understand the limits of flashes (speedlites). They don't do well at filling large modifiers. And when using a single flash, due to their rectangular head, they won't evenly fill round modifiers. There are things you can do to help, but that leads to less power output. Thus, it may be worth considering other brands of lighting gear (e.g. monolights).
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Ricky
Camera: EOS 5D IV, EF 50mm f/1.2L, EF 135mm f/2L
Lighting: Profoto Lights & Modifiers
