If you're spending less than $100k on marketing, stop worrying about attribution. Pick one channel, test it properly, and actually spend enough there to learn what works. Spreading thin across multiple channels wastes money you can't afford to waste.
If you're thinking about attribution software and you're spending less than 100k, something has gone terribly wrong. You're focused on the wrong thing. At that stage, it should be obvious what is working and what is not working. The reason it's not obvious is because you're taking 100k of spend and you're peanut buttering it across multiple channels and you're spraying and praying and hoping something works. So what would I do if I were in your shoes? I would pause all that spend. I would test each each channel one at a time to see if I can inflect whatever that metric is for success. Let's take Paramark's example. Our leading metric is demos booked on our website. If I'm going to do advertising, I'm going to do one channel at a time until I know it's proven. My message, my offer, my targeting, my distribution is awesome before I move to the next channel. And so I don't need attribution because I'm doing one channel at a time. There is nothing else to attribute. And if you do it that way, you build your layer cake and by the time you're done, your business is off to the races.