Hmm... You can get Tier 2 Dragon Bones and Tier 3 Runes from Ultimate Raids and 50 AP Daily Quests. I assume you don't have a lot of disposable Half-Elixirs or Prison of Element Idea Cores to start them? You can also trade lower tier mats from the gacha, lower AP Daily Quests and raids in the material exchange shop. Only nine T2 Bones or T3 Runes are needed for each element in a week. Getting all of them should be feasible unless I'm omitting something.
In that case here is a method to let you customize how many of each same-element and different-element Lv.1 SRs and SSRs to use
Start with 1 same-element R and 33 different-element SSR for a total of 34 fodder accessories to reach 13,345 EXP (150 + 33*400 = 150 + 13,200 = 13,350). The fodder accessory total count can be increased up to 40 and some of the different-element SSR can be substituted for different-element SRs and same-element SRs / SSRs. (You can use more than 40 fodder accessories if you have a lot of gems and don't mind the additional cost):
1) 2 Different-element SR can replace 1 diffrent-element SSR - Add 1 to the total fodder count each time you use this substitution
2) 4 Same-element SR can replace 3 different-element SSR - Add 1 to the total fodder count each time you use this substitution
3) 2 Same-element SSR can replace 3 different-element SSR - Deduct 1 from the total fodder count each time you use this substitution.