Any advice on marketing for a very low budget?

Definitely subscribe on the free plan at Qwoted.com so get mentions in media/journalists writings on subjects you are an expert in. Featured.com is another good resource to get noticed.

If you are a registered startups, Google offer free credits for Google ads for example. There are many program from lrge corporations to help early stage startups market their product by offering discounts or credits. Else, content creation through blog posts, social media posts, and cold outreach is what I'd do

Totally depends on the app. I would recommend to focus on content creation on YouTube, social media, plus blog to get traffic from Google.

Partnership, collaboration, and going to social media groups is a very good way to make your product visible

Incentivised referrals and app store optimisation (ASO).

track and measure

Thanks you all for the advice!

Focus on organic social media: Leverage platforms like Facebook, Instagram, Twitter, and LinkedIn to engage with your audience. Share valuable content, interact with your followers, and use relevant hashtags to increase visibility. Content marketing: Create high-quality, informative content that resonates with your target audience. This could include blog posts, videos, infographics, or podcasts. Share your content on your website and social media channels to attract and retain customers. Utilize email marketing: Build an email list of interested prospects and customers and regularly send out newsletters, promotions, and updates. Email marketing is cost-effective and can have a high ROI if done correctly. Collaborate with influencers or partners: Identify influencers or complementary businesses in your niche and collaborate with them on joint marketing efforts. This could involve guest blogging, co-hosting events, or cross-promoting each other's products or services. Optimize your website for SEO: Improve your website's search engine optimization (SEO) to increase organic traffic. Research relevant keywords, optimize your website's meta tags and content, and regularly publish fresh, high-quality content to improve your search engine rankings. Utilize free marketing tools and platforms: Take advantage of free marketing tools and platforms, such as Google My Business, Google Analytics, and social media management tools like Hootsuite or Buffer. These tools can help you manage and track your marketing efforts effectively. Networking and word-of-mouth: Attend industry events, join online communities and forums, and actively engage with potential customers and partners. Word-of-mouth marketing can be powerful and cost-effective, so focus on building relationships and delivering exceptional customer experiences.

Engage with people and users. Look into the "Founder Funnel" Strategy & Provide as much value as possible for free.

Use communities like reddit, quora, product hunt and more to get word of mouth going. Attend local events and be a spokesperson to your product. Run referral program and give app credits for successful referrals

LinkedIn can be very useful. I know many companies that have become known through LinkedIn posts. All other social media platforms are also very important tools.