Just level to 30. Even a mid elo player who is on an alt account (gold, maybe high silver since that's like top 1/3 of the ladder i think, maybe?) will go up pretty quick. The reason you're playing harder people on completely fresh accounts is because they haven't moved up, or they are low elo players who are trying to beat up on new players. Focus on getting to level 30 because it is such a huge difference to have runes/masteries, and even bronze level players are stronger than most new players. If you're wondering about strength, jump into the intermediate bots, from my experience (started the season bronze III) intermediate bots are maybe close to the level of difficulty you'll find against low bronze players. The bots are predictable so if you exploit that they're way easier, but if you aren't predicting bot behavior and just think about mechanical skill of the bots, and their ability to trade and fight, I'd say it's low bronze level. Get to where you can play intermediate bots games and consistently get 10-20 kills and no deaths. (Then you're probably bronzish level play, with a general knowledge base of the game and a solid foundation to really focus on improving in PVP.)
Biggest thing is just to focus on what you can do better each game, and what you did right that you need to keep doing. The game will move you to the skill level you need to be at, so it'll balance out eventually. (I played from bronze III to gold this season, and have a second account from leveling w/ a friend that was also bronze from my placements, and I really struggled in bronze at the start of the season, but am like 20-2 since jumping back down in elo just because I focused on getting better. Which is crazy considering I'm really not good, and just wanted to put the second account where it will get end of season rewards and then work on improving my play so I can consistently beat gold level games.