Slippage for backtesting

Hello, I am in the beginning phases of backtesting/developing some algo strategies for various instruments, on a couple of different brokers. Brokers would be Tradestation and Interactive Brokers (using Ninja Trader to connect the Tradestation strategies to Interactive Brokers). I am trying to get some information on average slippage for market orders. I know slippage depends on many factors, but we have to account for it during backtesting, otherwise a garbage strategy can look deceptively profitable.
Does anyone have data they would be willing to share for average slippage for these instruments? Or know where that information might be available? Again, I only need some approximate data that will help with backtesting. Thanks all.
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Butter - CB
Dry whey - DY
E-mini soybeans - YK
E-mini wheat - YW
Wheat - ZW

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S&P 500 Index - SPY
S&P 500 Dividend Points (Annual) Index - SPXDIVAN
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Russell 1000 ETF - IWB/RS1

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Micro Bitcoin - MBT

3-month Bloomberg Bank Yield - BSBY
Dow Jones US Real Estate Index - DJUSRE
Housing index composite - CUS

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Financial Select Sector Index - IXM
Consumer Staples Select Sector Index - IXR
Real Estate Select Sector Index - IXRE
Technology Select Sector Index - IXT
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Health Care Select Sector Index - IXV

5-Year Deliverable Interest Rate Swap Futures - F1U
2 Year Micro Treasury Yield - 2YY
5 Year Micro Treasury Yield - 5YY

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Altria - MO
Gilead - GILD
Phillips - PSX
Mastercard - MA
Viacom - VIAC

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