Describing how to value an item or thing

"appraise" is the best option. It's widely understood and synonymous with valuate.

"Buy, sell, and appraise your assets."

You can consider value, it is a common word in finance and it is understandable.

(It also covers all three words that you listed: estimate, assess, and appraise)

value: to calculate or reckon the monetary value of; give a specified material or financial value to; assess; appraise: to value their assets.

value: to determine or estimate the worth or value of; appraise.

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Buy, sell, and value your assets

You can consider rate also if there are different rating systems than just estimating the monetary value.

Assign a standard or value to (something) according to a particular scale

Flater's comment:

To be more clear: If you want to know which of your assets is the most valuable, you're rating them. If you want an idea of their combined worth, you're valuing them.

Rate describes a more comparative intent (you're measuring value specifically in comparison to others). If you value something, you're not inherently looking to compare it. So I guess its application depends on the intention of the measured value.