Newbie TFSA investor

Hello Everyone! Im a little late to the investing game but my wife and I have started to save a very small amount every month in a TD TFSA account. We have a tonne of contribution room in both our TFSAs and RRSPs. We currently have just under $900 in the account and I haven't invested the money in anything so far. I want to start but I was under the impression that I needed a minimum of $1000 to start.
I looked at WealthSimple a couple of days ago but couldn't get any info on what they would charge me to transfer over the TFSA account ($5000 and over they say they will wave the transfer fees - but Im not there yet). My thoughts were to keep the TFSA at TD until I reach $5000 and then maybe transfer over to Wealthsimple. Maybe I should just stick with TD?
I do have some basic knowledge about investing but not any real life experience so I just really wanted to get my feet wet and start regardless of how "little" Im working with. Im interested in long term investing, riding out highs and lows and continually investing steadily through every season. I want to invest as "high risk" as possible because its for the long term so I want to just ride out a group of index funds or ETFs until my portfolio grows a bit bigger and I get a feel for the process.

Questions:
1) Ive heard TD Direct Investing is different than just buying a simple investment (buy and hold) but I don't understand how to just purchase an investment directly out of my TFSA without getting into managed funds (managed by TD that is). I don't really want an advisor at this point until I feel more comfortable and have more info
2) Wealthsimple (or other ROBO) better investment vehicle than TD? Any idea what the fees are to transfer to another institution? (tried contacting both TD and WealthSimple and either got hung up on after on hold for an hour or not responded to by email.... this also kind of concerns me but I do understand this is a crazy time)
3) Borrowing to invest during a market downturn (like Coronavirus)? We have a LOT of available credit but I know its very risky to borrow money to invest