Since the q nerfs, and with the current meta where early kills are heavily nerfed as they give less gold and exp and don't give firsts blood gold, cheese invades feel terrible.

I agree with Hybradge, he has a great guide on Bel on youtube and he's EUW chall,that to consistently climb, fullclearing is the way. And generally, fullclearing towards bot. You can get your clear down to 3:1O starting blue side and thats huge.

You full clear towards bot twice, on time, taking your respawn camps as they spawn, pinging your team to avoid where you think enemy will gank and if the enemy wastes time you're naturally ahead. Your goal isn't to get dragons early, as without level 6 or kraken you do drakes very slow and will fall behind doing them - unless your lanes are super winning and leash you. Your goal is to punish the enemy for trying to gank for drake or even starting it so you can get kills, thats much more important for bel than first drake as she needs gold.

For grubs, you only need one grub for form, then if its at all risky you can just leave, its never worth flipping and dying to lose form for 2 or 3 grubs. Bel is really good at killing one grub fast with smite into E, but it takes her a lot longer to do all 3 which is where bel's get punished. If you are trading grubs and drake, you can one shot the second grub with smite + R coral from the first grub.

After you have true form, drakes become much easier to take and useful as they extend your true form. You can dash over the pit to find flanks on bot or mid or the enemy jungle to setup drakes. And if a drake is ever risky, you can just play for the enemy topside camps, or a gank on mid or top that leads into a lot of plates due to your true form minions. Bel'veths win con is a lead in gold and exp so she can carry, she can go down 3 drakes and it doesn't matter as long as she's ahead.

With rift, a common play is to rift top lane and go for 2 towers while the enemy gets drake, that usually wins you the game as the enemy jungle will never be able to fight you again and you own the map, including all future drakes. Just make sure you communicate with your team you won't be playing for drake so they don't die contesting it. They will flame you, ignore them and carry.