There is no one-size-fits-all answer, as digital marketing budgets vary greatly based on factors like business size, industry, goals, and geographic market. However, here are some general guidelines on establishing a decent budget:

• For small businesses, $2,000 to $5,000 per month is recommended to cover the essentials like search ads, social media marketing, content creation, etc.
• For medium sized companies, $5,000 to $15,000 per month allows for an expanded presence including retargeting ads, lead generation campaigns, basic analytics, etc.
• Enterprises need $15,000 to $25,000+ per month to leverage the full suite of digital channels at higher spending levels plus martech tools.
• Allocate at least 10-20% of estimated gross revenue for digital activities. Divide into monthly or quarterly budgets.
• When starting out, err on the side of more budget to test and optimize various strategies. Cut back on poor performing areas later.
• Dedicate most budget to 2-3 core high return activities rather than spreading thinly across too many campaigns.
• Factor in in-house vs outsourced costs. Specialists like web developers may warrant higher spending.
• Monitor results continuously and expand budgets for campaigns that are generating positive ROI. Reduce ineffective areas.
• Keep some budget flexibility to take advantage of new opportunities that arise during execution.

Achieving an optimal digital marketing budget takes some experience and continuous tweaking based on data. But following industry benchmarks gives a reasonable starting point.