How much ram will I need for 1.14.4 paper spigot with 30 players at the same time

Hello, i have a 1.14.4 paper spigot server with 5gb of ram. i followed the spigot official guide for optimization, and im using world border. My server works well at 20 tps with 15 people but when i get 18+ people the tps start to drop to 18 and 17, i sent the timings to my host and they said it wasnt lag of the plugins , it was just minecraft lag. So they told me to upgrade the package to 6gb of ram and a better CPU , but i cant afford to pay more of the actual plan i have. And i read here that some are good with 4gb of ram , so i wish if is there any way to keep my server at 20 tps with 30 people at the same time.

i have optimized this things as a guide in internet

  • Mᴀᴘ Pʀᴇ-Gᴇɴ
  • Bᴜᴋᴋɪᴛ.ʏᴍʟ
  • Sᴘɪɢᴏᴛ.ʏᴍʟ
  • Pᴀᴘᴇʀ.ʏᴍʟ
  • Sᴇʀᴠᴇʀ.Pʀᴏᴘᴇʀᴛɪᴇs

and i have this plugins for optimization:

  • [Fix Pillager Lag (free)
  • [Fix Villager Lag (free)
    -SAML
    also i disabled the pillager raids in gamerules

The current cpu i have is Xeon E5-1630v3 @ 3.7Ghz with 5gb of ram
and they told me to upgade to Xeon E5-1650v3 @ 3.8Ghz with 6gb of ram

and im running paper spigot 1.14.4 (build: 225)

this are some pictures of the timings, sorry if i dont post the link:
https://gyazo.com/946ab070b0b8f8c8a37b95e2b1c66951
https://gyazo.com/0e14322b5c7800b946b4e1e66748540f
https://gyazo.com/01fdcaddcf78a638770579e92ae397ad

(sorry if i wrote something wrong, im still learning english)