If you have a way to intentionally ping your own creatures, Silverclad Ferocidons can clear out a lot of the board for you
Finally, starter decks come with a single booster pack of 12 random cards
Fire Nation Salvagers can help reanimate multiple cards each combat in a counters deck, provided opponents have them available
In my years of personal experience, examining good decklists, and talking to people much smarter than me, 50 mana sources is about the right number for most decks to shoot for, usually 37 lands and 13 ramp sources for a general budget deck
Alenni, Brood Recruiter Baru, Fist of Krosa Battle Frenzy Boartusk Liege Cabaretti Charm Catharsis Creakwood Liege Deranged Hermit Glistening Deluge Howlpack Alpha Imperious Perfect Juniper Order Advocate Jyoti, Moag Ancient Kaysa Kinbinding Meng Huo, Barbarian King Murkfiend Liege Nemata, Grove Guardian Nissa, Ascended Animist Paragon of Eternal Wilds Phabine, Boss's Confidant Plane-Merge Elf (playtest) Rank and File Restless Prairie Rouse the Swarm Selesnya Guildmage Silk, Web Weaver Squirrel Wrangler Sylvan Anthem Thelonite Hermit Tolsimir Wolfblood Verdeloth the Ancient Wall Crawl Wilt-Leaf Liege