3-Pack of TP-Link Kasa HS200 Smart Wifi Light Switches for $35 ($11.67 each). Shows as $40, and click the extra $5 coupon checkbox in the middle of the page.
Each of these replace existing light switches on your wall, and require an electrician to install. Angi.com is a good place to find a local electrician.
Electricians can charge anywhere from $20 to $50 per switch install, which is not cheap. Some electricians charge by the hour, which would likely be pricier than a per-switch fixed price. So, beware of the true cost for you to install smart switches versus getting smart bulbs and smart wall outlets.
We like Kasa switches, and compared them all: Kasa HS200 on/off switches (the 3-pack deal) are on/off switches, with no dimming capabilities. They support up to 300W max load (150W LED), meaning it can control a lot of lights on a single switch. Kasa HS220 dimmable switches is the dimmable model, with a major drawback. It supports up to 150W max load (75W LED), so a switch controlling 6 bulbs or more may push the switch beyond its limit, causing a safety hazard. Also, not every LED bulb supports dimming, and could cause damage when using non-dimmable LED bulbs on a dimming switch. Kasa HS210 3-way switches includes 2 switches per pack. They are functionally identical to the HS200 with a max wattage of 300W, and guaranteed to work with 3-way wiring. All can be controlled with the free Kasa app, and with Google and Amazon smart speakers. They work with regular 2.4GHz wifi (not 5GHz).