For free tracking, http://analytics.google.com is your go-to; it handles conversions, mobile/desktop splits, and basic keyword tracking, though digging into granular ppc data can feel like solving a puzzle. Pair it with UTM parameters (use Google’s free Campaign URL Builder) to tag campaigns like a pro. If you’re cheap but want slightly more juice, http://clarity.microsoft.com offers session recordings and heatmaps for free, great for spotting user behavior hiccups.
For paid options, Google Ads and Microsoft bake in solid tracking for keywords, day parting, and device stats, but if you’re running cross-network chaos (Google, Bing, social, etc.), http://clickmagick.com is budget-friendly (~$20/month) and tracks everything, rotating banners, split tests, even suspicious clicks. Need enterprise-level muscle? http://voluum.com crunches data across 50+ ad networks, offers geotargeting reports, and automates campaign tweaks. Also, http://tagmanager.google.com is free and lets you slap tracking codes everywhere without coding.