What should I include in my product marketing budget?

You have all the right line items! In addition, I'd recommend:

• Focus groups for messaging/positioning/pricing & packaging: I'm a huge fan of getting feedback from prospects and customers on any new changes. This helps to have impactful content. 
• Video editor/agency: Having a 3rd party video editor helps speed up content creation considerably. Plus, they can usually handle multiple projects at the same time and you can create new sales or external-facing collateral pretty fast.
• Tool to track sales content adoption: Highly recommend a tool to track content adoption by your sales team. Helps you understand what kind of content sticks with your sales team to double down. 

A few other things to consider:

• Your team's research needs (qual and/or quant) 
• Any analyst-related spent (either for research reports or to engage w/ analysts)
• Content-related needs -- always a good idea to work with a good content agency to flex your capacity when needed
• And perhaps most important - a team-building/fun budget for your team :)

Aim high, and ask for more than you think you'll need - but not by more than 15-20%. People will always be your biggest budget line item in PMM - we're the most valuable asset because structured thinking and positioning can't really be outsourced or delegated to software.

However, key items that I would examine for fit in your budget:

• Content creation for top-of-funnel assets, separate from Content Marketing
• Video production (think $5-10K for an animated explainer video) to fill in gaps in your content
• Competitive and market survey data. Plan ahead to learn more about your customers

Sales Enablement: Can you co-fund sales training and methodology off-cycle from SKO?

This is a good list to start with. I will add a couple:

• Analyst/3rd party thought leadership pieces: Having independent, 3rd party content is very helpful. If you are focused on the Enterprise, having content from top tier analysts is helpful. I have worked with Gartner, Forrester, The 451 Group, Ovum Research and IDC in the past
• Graphics/multimedia: you will need to generate lots of great content that you deploy across channels. You may have good writing skills in your team but you will likely need support for research/graphics/multimedia. I have typically relied on external agencies.
• PR: The world has changed, but this remains a very important avenue to get your message out. I have found that working with PR experts is both more effective and less expensive, but it depends on your budget and the market you are going after.

Great question. Looks like you've captured a lot of the big rocks that normally go into the budget, but a few additional things to consider:

• People Budget: Depending on the planned growth of your team for this year, and near-term priorities, knowing your people budget can ensure you can bring in consultants (as necessary) to bridge any gaps and help support short-term strategic initiatives. 
• Tools: Beyond Sales Enablement/Content Management, you may want to consider Competitive Intelligence as another tool category if you don't have one already.
• Win/Loss: If you're not already doing win/loss interviews internally, there are some external firms that can help conduct deep-dives into why you're winning or losing potential deals. This insight can and should directly feed into virtually everything you're doing across Product Marketing.
• Team Events/Relationship Building: If you're remote, or hybrid, as a leader you'll need to be intentional about growing relationships within your team, and cross-functionally as well. So be sure to set some budget aside for team events, get togethers, and celebrating milestones.
• Discretionary: In my experience, you can budget for a lot of major pieces, but ensure you have some discretionary budget set aside for things that emerge -- such as driving reviews with gift cards for example. 

These are just a few ideas, but hopefully they help create a full picture of what you'll need to think about for your budget. Keep in mind this is an art and a science so work with leadership and plan effectively, and learn quarter over quarter to ensure you have the resources needed for success of your team and the overall business. 

Love what you have already! Do you have budget for qual research incentives? This is a huge gift if you can offer $100 to target personas to provide feedback on messaging, or to prospects for win/loss interviews, etc. Also consider a recruiting tool like Respondent.io if you are running out of low-hanging fruit from networking / site pop-ups / LinkedIn recruiting.  

I would recommend doing a listening tour with your key stakeholder teams in the organization (product, sales, growth, enablement, partner) to help inform your priorities, as budget items could be almost limitless. It's also important to understand the state of your product and where it might need the most help, to help prioritize your asks. E.g you might need to invest more in awareness / thought leadership content or third party validation research, or maybe you have needs lower in the funnel such as demo and video creation.

Some good buckets could be: content creation (white papers, webinars, etc.), videos / demos, customer evidence, event sponsorships, research (pricing, naming, thought leadership, competitive, etc.), sales readiness (decks, demos, sales process / methodology guidance and training, RFP templates), launch (could be captured in other buckets but may include 1st party events, press events, content creation).

I think that list is correct and you should prioritize this list depending on your business. In addition to the above, I would advise getting a tool like Chorus.ai or Gong.io. Chorus or Gong will help you scale as your team scales in getting customer feedback both on the new business side as well as current business. In reality, you can't be on all the great calls as that is physically impossible.